A cooperative control method of a solid-state transformer cluster system

Abstract

This invention discloses a collaborative control method for a solid-state transformer cluster system. The method includes: detecting whether a new SST (Solid State Transformer) is powered on and connected to the common AC bus; if so, first triggering the new SST to broadcast a "Hello" data packet containing its ID and rated capacity to all online SSTs; then triggering the first online SST to receive the data packet to send a "Challenge" data packet containing a random number to the new SST; next, signing the random number using the new SST's pre-stored private key and returning it to the first online SST to receive the "Hello" data packet; then verifying the signature using the SST's pre-stored public key; after successful verification, synchronizing the new SST's ID and rated capacity to all other online SSTs in the cluster. This invention solves the problem in the current collaborative control system of solid-state transformer clusters where, when a new solid-state transformer is connected to the system, the system cannot automatically identify its device identity and other parameters, requiring the entire system to be shut down and undergoing cumbersome software configuration and parameter tuning operations.

Description

Technical Field

[0001] This invention relates to the field of solid-state transformer cluster control technology, specifically a collaborative control method for solid-state transformer clusters. Background Technology

[0002] Solid-state transformers (SSTs), as core equipment for next-generation power conversion, have broad application prospects in fields such as AC / DC hybrid power distribution and new energy grid connection. In practical engineering applications, to meet the needs of system expansion and redundancy backup, multiple SSTs are usually connected in parallel to form a SST cluster system. However, under the current collaborative control system of SST cluster systems, when a new SST is connected to the system, the system cannot automatically identify its equipment identity, rated capacity, and other key parameters. This often requires shutting down the entire system and performing cumbersome software configuration and parameter tuning operations, thus affecting the availability and maintainability of the system. Summary of the Invention

[0003] To address the aforementioned shortcomings, this invention proposes a collaborative control method for a solid-state transformer cluster system. The aim is to solve the problem that in the current collaborative control system for solid-state transformer clusters, when a new solid-state transformer is connected to the system, the system cannot automatically identify its equipment identity, rated capacity, and other parameters, which usually requires shutting down the entire system and performing cumbersome software configuration and parameter tuning operations.

[0004] To achieve this goal, the present invention adopts the following technical solution: A collaborative control method for a solid-state transformer cluster system, wherein the solid-state transformer cluster system consists of several solid-state transformers (SSTs) connected in parallel to a common AC bus, each SST including a controller, a voltage loop, a current loop, and power devices, the method comprising the following steps: Step S1: Check if a new SST is powered on and connected to the common AC bus. If not, proceed directly to steps S2-S5. If yes, first trigger the new SST to send a "Hello" data packet to all online SSTs. The "Hello" data packet includes the new SST's unique identifier ID and rated capacity. Then, trigger the first online SST to receive the "Hello" data packet to send a "Challenge" data packet to the new SST. The "Challenge" data packet includes a random number. Next, use the private key pre-stored in the new SST controller to sign the random number in the "Challenge" data packet and send the signature to the first online SST to receive the "Hello" data packet. Then, use the public key pre-stored in the controller of the first online SST to receive the "Hello" data packet to verify the signature. If the verification is successful, send the new SST's ID and rated capacity to all other online SSTs to update the preset online SST list in each online SST. Finally, execute steps S2-S5 based on the updated online SST list. Step S2: Using a distributed consensus algorithm, calculate the unitized power of each online SST. And the global normalized power average of all online SSTs. ; Step S3: According to and The power error of each online SST was calculated. ,in, The specific calculation formula is as follows: ; Step S4: Obtain the virtual resistance and virtual inductance of each online SST, and calculate the virtual impedance of each online SST based on the virtual resistance, virtual inductance and power error of each online SST. Step S5: Input the virtual impedance of each online SST into the voltage loop of the corresponding SST to generate the current reference command for each online SST; and input the current reference command of each online SST into the current loop of the corresponding SST to generate the pulse width modulation signal for each online SST to drive the power device of the corresponding SST to operate.

[0005] Preferably, in step S2, the unitized power of each online SST is... The specific calculation formula is as follows: ; in, This represents the local output active power of the i-th online SST; This represents the rated capacity of the i-th online SST.

[0006] Preferably, in step S2, a distributed consensus algorithm is used to calculate the global unitized power average of all online SSTs. Specifically, it includes the following sub-steps: Step S21: Set the local state variables for each online SST, and set the initial value of the local state variables for each online SST to its own unitized power. ; Step S22: Update and iterate the local state variables of each online SST until the local state variables of each online SST converge to the same value. and will Determined as the global normalized power average The mathematical expression for updating the local state variables of each online SST is as follows: ; in, This represents the local state variable of the i-th online SST during the k-th iteration; Indicates connection weight; This indicates that the j-th neighboring SST of the i-th online SST is at its most recent trigger time. Local state variables; Let SST represent the set of neighboring SSTs of the i-th online SST.

[0007] Preferably, step S2 further includes the following step: When the local state variable of the i-th online SST meets the preset trigger condition, the online SST broadcasts its current state information to its neighboring SSTs. The preset trigger condition is as follows: ; in, Let represent the local state variable of the i-th online SST at time t; This indicates that the i-th station is online at the time of its most recent trigger. Local state variables; This represents the dynamic threshold configured for the i-th online SST.

[0008] Preferably, in step S4, the specific calculation formula for the virtual impedance of each online SST is as follows: ; ; ; in, This represents the virtual impedance of the i-th online SST during the m-th control cycle. This represents the virtual resistance of the i-th online SST during the m-th control cycle; This represents the virtual inductance of the i-th online SST during the m-th control cycle; This represents the integral coefficient corresponding to the virtual resistance; This represents the integral coefficient corresponding to the virtual inductance; This represents the power error of the i-th online SST during the (m-1)-th control cycle; Represents a symbolic function; This represents the local output active power of the i-th online SST; This represents the local output reactive power of the i-th online SST.

[0009] Preferably, in step S5, the virtual impedance of each online SST is input into the voltage loop of the corresponding SST to generate a current reference command for each online SST, specifically including the following sub-steps: Step S51: Measure and obtain the output current of the i-th online SST. and output voltage Simultaneously, obtain the rated voltage reference value of the i-th online SST. The proportional gain of the voltage loop PI controller and the integral gain of the voltage loop PI controller ; Step S52: According to The virtual impedance of the i-th online SST The virtual impedance voltage drop of the i-th online SST is calculated. ,in, The specific calculation formula is as follows: ; Step S53: According to , , , and The current reference command for the i-th online SST is calculated. ,in, The specific calculation formula is as follows: ; Where s represents the Laplace operator.

[0010] The technical solution provided by this invention may include the following beneficial effects: In this scheme, when a new SST is detected to be powered on and connected to the public AC bus, it first broadcasts a "Hello" data packet containing its ID and rated capacity to all online SSTs. Then, the first online SST to receive this packet sends a "Challenge" data packet containing a random number to the new SST. Next, the random number is signed using the new SST's pre-stored private key and returned to the first online SST to receive the "Hello" data packet. The signature is then verified using the SST's pre-stored public key. Upon successful verification, the new SST's ID and rated capacity are synchronized to all other online SSTs in the cluster, thus achieving automatic identification and parameter synchronization of the new SST. The entire process requires no system downtime and no manual, cumbersome software configuration or parameter tuning, effectively improving system availability and maintainability. Attached Figure Description

[0011] Figure 1 This is a flowchart illustrating the steps of a collaborative control method for a solid-state transformer cluster system. Detailed Implementation

[0012] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0013] A collaborative control method for a solid-state transformer cluster system, wherein the solid-state transformer cluster system consists of several solid-state transformers (SSTs) connected in parallel to a common AC bus, each SST including a controller, a voltage loop, a current loop, and power devices, the method comprising the following steps: Step S1: Check if a new SST is powered on and connected to the common AC bus. If not, proceed directly to steps S2-S5. If yes, first trigger the new SST to send a "Hello" data packet to all online SSTs. The "Hello" data packet includes the new SST's unique identifier ID and rated capacity. Then, trigger the first online SST to receive the "Hello" data packet to send a "Challenge" data packet to the new SST. The "Challenge" data packet includes a random number. Next, use the private key pre-stored in the new SST controller to sign the random number in the "Challenge" data packet and send the signature to the first online SST to receive the "Hello" data packet. Then, use the public key pre-stored in the controller of the first online SST to receive the "Hello" data packet to verify the signature. If the verification is successful, send the new SST's ID and rated capacity to all other online SSTs to update the preset online SST list in each online SST. Finally, execute steps S2-S5 based on the updated online SST list. Step S2: Using a distributed consensus algorithm, calculate the unitized power of each online SST. And the global normalized power average of all online SSTs. ; Step S3: According to and The power error of each online SST was calculated. ,in, The specific calculation formula is as follows: ; Step S4: Obtain the virtual resistance and virtual inductance of each online SST, and calculate the virtual impedance of each online SST based on the virtual resistance, virtual inductance and power error of each online SST. Step S5: Input the virtual impedance of each online SST into the voltage loop of the corresponding SST to generate the current reference command for each online SST; and input the current reference command of each online SST into the current loop of the corresponding SST to generate the pulse width modulation signal for each online SST to drive the power device of the corresponding SST to operate.

[0014] This solution proposes a collaborative control method for a solid-state transformer cluster system, such as... Figure 1As shown, in this embodiment, in the solid-state transformer cluster system, the controllers of each SST communicate via a wireless mesh network based on IEEE 802.15.4 or power line carrier, exchanging limited information only with their adjacent SSTs. No central controller is required, achieving a fully distributed architecture. In the method, the first step is to detect if a new SST is powered on and connected to the common AC bus. If not, steps S2-S5 are executed directly. If so, the new SST is first triggered to send a "Hello" data packet to all online SSTs, where the "Hello" data packet includes the new SST's unique identifier ID and rated capacity. Then, the first online SST to receive the "Hello" data packet is triggered to send a "Challenge" data packet to the new SST, where the "Challenge" data packet includes a random number. Next, the random number in the "Challenge" data packet is signed using a private key pre-stored in the new SST controller, and the signature is sent to... The first online SST to receive the "Hello" data packet is then used to verify the signature using the public key pre-stored in the controller of the first online SST to receive the "Hello" data packet. If the verification passes, the new SST's ID and rated capacity are sent to all other online SSTs to update the preset online SST list in each online SST. Finally, steps S2-S5 are executed based on the updated online SST list. In this embodiment, when a new SST is powered on and connected to the common AC bus, the new SST sends a "Hello" data packet containing its ID and rated capacity to all online SSTs, ensuring that the online SSTs can quickly obtain the core parameters of the new SST. By having the first online SST to receive the "Hello" data packet send a "Challenge" data packet containing a random number to the new SST, the uniqueness and randomness of the random number can effectively prevent replay attacks and ensure the security of the cluster system access. By signing a random number using the private key in the new SST controller and verifying the signature using the public key in the first online SST controller to receive the "Hello" data packet, unauthorized devices can be effectively prevented from accessing the cluster system, thereby improving the security and anti-interference capabilities of the cluster system. The ID and rated capacity of the new SST whose signature verification is successful are synchronized to other online SSTs by the first online SST to receive the "Hello" data packet, ensuring that the cluster system can monitor the legitimate authentication status of all currently online SSTs in real time. Furthermore, during the verification process using the public key pre-stored in the controller of the first online SST to receive the "Hello" data packet, if the verification fails, the access of the new SST is rejected. The second step involves using a distributed consensus algorithm to calculate the unitized power of each online SST. And the global normalized power average of all online SSTs. In this embodiment, a distributed consensus algorithm is used to calculate the unitized power of each online SST and the global average unitized power of all online SSTs. This eliminates the need for a central controller to coordinate the calculations, avoiding the single-point-of-failure risk associated with centralized control. Even if a single SST experiences a calculation anomaly, it will not affect the power parameter calculations of the entire cluster system. The third step is based on... and The power error of each online SST was calculated. ,in, The specific calculation formula is as follows: In this embodiment, by calculating the power error of each online SST, the deviation of the local power distribution status from the average level of the cluster's global unitized power can be accurately reflected, providing a reliable basis for the subsequent dynamic adjustment of virtual impedance. The fourth step is to obtain the virtual resistance and virtual inductance of each online SST, and calculate the virtual impedance of each online SST based on the virtual resistance, virtual inductance, and power error. In this embodiment, by combining the virtual resistance, virtual inductance, and power error of each SST to calculate its virtual impedance, the virtual impedance of each SST can be dynamically adjusted, thereby flexibly controlling the output characteristics of each SST, and ultimately achieving a balanced distribution of the output power of all SSTs in the solid-state transformer cluster system. The fifth step is to input the virtual impedance of each online SST into the voltage loop of the corresponding SST to generate a current reference command for each online SST; and then input the current reference command of each online SST into the current loop of the corresponding SST to generate a pulse width modulation signal for each online SST, so as to drive the power device of the corresponding SST to operate. In this embodiment, by first inputting the virtual impedance of the SST into the voltage loop of the SST and generating a current reference command, and then inputting it into the current loop of the SST to generate a pulse width modulation signal to drive the power device of the SST, the operating state of the power device of the SST can accurately respond to the power distribution requirements.

[0015] In this scheme, when a new SST is detected to be powered on and connected to the public AC bus, it first broadcasts a "Hello" data packet containing its ID and rated capacity to all online SSTs. Then, the first online SST to receive this packet sends a "Challenge" data packet containing a random number to the new SST. Next, the random number is signed using the new SST's pre-stored private key and returned to the first online SST to receive the "Hello" data packet. The signature is then verified using the SST's pre-stored public key. Upon successful verification, the new SST's ID and rated capacity are synchronized to all other online SSTs in the cluster, thus achieving automatic identification and parameter synchronization of the new SST. The entire process requires no system downtime and no manual, cumbersome software configuration or parameter tuning, effectively improving system availability and maintainability.

[0016] Preferably, in step S2, the unitized power of each online SST is... The specific calculation formula is as follows: ; in, This represents the local output active power of the i-th online SST; This represents the rated capacity of the i-th online SST.

[0017] In this embodiment, the unitized power of each online SST is obtained by comparing its local output active power with its corresponding rated capacity. This allows online SSTs with different rated capacities to be compared and controlled on the same scale, avoiding power distribution deviations caused by different rated capacities.

[0018] Preferably, in step S2, a distributed consensus algorithm is used to calculate the global unitized power average of all online SSTs. Specifically, it includes the following sub-steps: Step S21: Set the local state variables for each online SST, and set the initial value of the local state variables for each online SST to its own unitized power. ; Step S22: Update and iterate the local state variables of each online SST until the local state variables of each online SST converge to the same value. and will Determined as the global normalized power average The mathematical expression for updating the local state variables of each online SST is as follows: ; in, This represents the local state variable of the i-th online SST during the k-th iteration; Indicates connection weight; This indicates that the j-th neighboring SST of the i-th online SST is at its most recent trigger time. Local state variables; Let SST represent the set of neighboring SSTs of the i-th online SST.

[0019] In this embodiment, in step S21, the initial value of the local state variable of each online SST is set to its own unitized power. This provides the foundation for subsequent distributed iterative updates. In step S22, through iterative updates, the local state variables of each online SST eventually converge to the same globally normalized power average. This enables each online SST to accurately perceive the average power status of the entire cluster without the need for a central controller, achieving distributed sharing of global information.

[0020] Preferably, step S2 further includes the following step: When the local state variable of the i-th online SST meets the preset trigger condition, the online SST broadcasts its current state information to its neighboring SSTs. The preset trigger condition is as follows: ; in, Let represent the local state variable of the i-th online SST at time t; This indicates that the i-th station is online at the time of its most recent trigger. Local state variables; This represents the dynamic threshold configured for the i-th online SST.

[0021] In this embodiment, Set to 0.01. This is achieved by satisfying the local state variable of only the i-th online SST. Only when the trigger condition is met will the status information be broadcast to its neighboring SST. This can effectively reduce unnecessary communication overhead, thereby reducing network bandwidth usage and node energy consumption.

[0022] Preferably, in step S4, the specific calculation formula for the virtual impedance of each online SST is as follows: ; ; ; in, This represents the virtual impedance of the i-th online SST during the m-th control cycle. This represents the virtual resistance of the i-th online SST during the m-th control cycle; This represents the virtual inductance of the i-th online SST during the m-th control cycle; This represents the integral coefficient corresponding to the virtual resistance; This represents the integral coefficient corresponding to the virtual inductance; This represents the power error of the i-th online SST during the (m-1)-th control cycle; Represents a symbolic function; This represents the local output active power of the i-th online SST; This represents the local output reactive power of the i-th online SST.

[0023] In this embodiment, when When the unitized power of the i-th online SST is lower than the global average power level, the virtual impedance of the i-th online SST will automatically decrease, allowing it to output more power under the same voltage difference, thus keeping up with the global average power level. When the unitized power of the i-th online SST is higher than the global average power level, the virtual impedance of the i-th online SST will automatically increase to limit its output power, prevent overload operation, and ensure system stability. Further explanation... and All are positive numbers. When hour, ;when hour, .when hour, ;when hour, .

[0024] Preferably, in step S5, the virtual impedance of each online SST is input into the voltage loop of the corresponding SST to generate a current reference command for each online SST, specifically including the following sub-steps: Step S51: Measure and obtain the output current of the i-th online SST. and output voltage Simultaneously, obtain the rated voltage reference value of the i-th online SST. The proportional gain of the voltage loop PI controller and the integral gain of the voltage loop PI controller ; Step S52: According to The virtual impedance of the i-th online SST The virtual impedance voltage drop of the i-th online SST is calculated. ,in, The specific calculation formula is as follows: ; Step S53: According to , , , and The current reference command for the i-th online SST is calculated. ,in, The specific calculation formula is as follows: ; Where s represents the Laplace operator.

[0025] In this embodiment, in step S51, the measurement is obtained. and and obtain , and This provides reliable input data for subsequent calculations of virtual impedance voltage drop and current reference commands. Further explanation: by obtaining... and This allows the dynamic response characteristics of the voltage loop to be flexibly adjusted according to system operating conditions, thereby improving the adaptability of the control strategy. In step S52, the virtual impedance voltage drop of the i-th online SST is calculated. This allows the abstract virtual impedance to be transformed into a quantifiable voltage drop, thus making the concept of "virtual impedance" concrete in the SST control loop. In step S53, the current reference command for the i-th online SST is calculated. During the process, voltage error is controlled by adjusting the proportional gain and integral gain of the voltage loop PI controller. The adjustment can quickly respond to dynamic changes and eliminate steady-state errors, ensuring that the output voltage accurately tracks the reference value.

[0026] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0027] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A collaborative control method for a solid-state transformer cluster system, wherein the solid-state transformer cluster system consists of several solid-state transformers (SSTs) connected in parallel to a common AC bus, and each SST includes a controller, a voltage loop, a current loop, and power devices, characterized in that: The method includes the following steps: Step S1: Check if a new SST is powered on and connected to the common AC bus. If not, proceed directly to steps S2-S5. If yes, first trigger the new SST to send a "Hello" data packet to all online SSTs. The "Hello" data packet includes the new SST's unique identifier ID and rated capacity. Then, trigger the first online SST to receive the "Hello" data packet to send a "Challenge" data packet to the new SST. The "Challenge" data packet includes a random number. Next, use the private key pre-stored in the new SST controller to sign the random number in the "Challenge" data packet and send the signature to the first online SST to receive the "Hello" data packet. Then, use the public key pre-stored in the controller of the first online SST to receive the "Hello" data packet to verify the signature. If the verification is successful, send the new SST's ID and rated capacity to all other online SSTs to update the preset online SST list in each online SST. Finally, execute steps S2-S5 based on the updated online SST list. Step S2: Using a distributed consensus algorithm, calculate the unitized power of each online SST. And the global normalized power average of all online SSTs. ; Step S3: According to and The power error of each online SST was calculated. ,in, The specific calculation formula is as follows: ； Step S4: Obtain the virtual resistance and virtual inductance of each online SST, and calculate the virtual impedance of each online SST based on the virtual resistance, virtual inductance and power error of each online SST. Step S5: Input the virtual impedance of each online SST into the voltage loop of the corresponding SST to generate the current reference command for each online SST; and input the current reference command of each online SST into the current loop of the corresponding SST to generate the pulse width modulation signal for each online SST to drive the power device of the corresponding SST to operate.

2. The collaborative control method for a solid-state transformer cluster system according to claim 1, characterized in that: In step S2, the unitized power of each online SST is... The specific calculation formula is as follows: ； in, This represents the local output active power of the i-th online SST; This represents the rated capacity of the i-th online SST.

3. The collaborative control method for a solid-state transformer cluster system according to claim 2, characterized in that: In step S2, a distributed consensus algorithm is used to calculate the global unitized power average of all online SSTs. Specifically, it includes the following sub-steps: Step S21: Set the local state variables for each online SST, and set the initial value of the local state variables for each online SST to its own unitized power. ; Step S22: Update and iterate the local state variables of each online SST until the local state variables of each online SST converge to the same value. and will Determined as the global normalized power average The mathematical expression for updating the local state variables of each online SST is as follows: ； in, This represents the local state variable of the i-th online SST during the k-th iteration; Indicates connection weight; This indicates that the j-th neighboring SST of the i-th online SST is at its most recent trigger time. Local state variables; Let SST represent the set of neighboring SSTs of the i-th online SST.

4. The collaborative control method for a solid-state transformer cluster system according to claim 3, characterized in that: Step S2 also includes the following steps: When the local state variable of the i-th online SST meets the preset trigger condition, the online SST broadcasts its current state information to its neighboring SSTs. The preset trigger condition is as follows: ； in, Let represent the local state variable of the i-th online SST at time t; This indicates that the i-th station is online at the time of its most recent trigger. Local state variables; This represents the dynamic threshold configured for the i-th online SST.

5. The collaborative control method for a solid-state transformer cluster system according to claim 1, characterized in that: In step S4, the specific calculation formula for the virtual impedance of each online SST is as follows: ； ； ； in, This represents the virtual impedance of the i-th online SST during the m-th control cycle. This represents the virtual resistance of the i-th online SST during the m-th control cycle; This represents the virtual inductance of the i-th online SST during the m-th control cycle; This represents the integral coefficient corresponding to the virtual resistance; This represents the integral coefficient corresponding to the virtual inductance; This represents the power error of the i-th online SST during the (m-1)-th control cycle; Represents a symbolic function; This represents the local output active power of the i-th online SST; This represents the local output reactive power of the i-th online SST.

6. The collaborative control method for a solid-state transformer cluster system according to claim 1, characterized in that: In step S5, the virtual impedance of each online SST is input into the voltage loop of the corresponding SST to generate a current reference command for each online SST. This includes the following sub-steps: Step S51: Measure and obtain the output current of the i-th online SST. and output voltage Simultaneously, obtain the rated voltage reference value of the i-th online SST. The proportional gain of the voltage loop PI controller and the integral gain of the voltage loop PI controller ; Step S52: According to The virtual impedance of the i-th online SST The virtual impedance voltage drop of the i-th online SST is calculated. ,in, The specific calculation formula is as follows: ； Step S53: According to , , , and The current reference command for the i-th online SST is calculated. ,in, The specific calculation formula is as follows: ； Where s represents the Laplace operator.

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