Converter seamless transfer method based on stst fast turn-off

Abstract

The application relates to the fields of power electronic technology and power quality treatment technology, and discloses a seamless switching method of a converter based on a transient voltage injection STS fast turn-off, which directly generates a forced current component opposite to the original current direction in the STS loop by injecting a designed transient turn-off voltage into an output end of an energy storage converter, so that the STS current is actively and quickly offset to make it quickly zero-cross and turn off; meanwhile, double feedforward control of a load current and a grid-connected point voltage is introduced to realize decoupling of a commutation process and system disturbance, further reduce a response time, and realize seamless switching of the energy storage converter between grid connection and off-grid.

Description

Technical Field

[0001] This invention relates to the fields of power electronics technology and power quality management technology, specifically to a seamless switching method for converters based on transient voltage injection STS fast turn-off. Background Technology

[0002] As a key device connecting energy storage units and the power grid, the energy storage converter can provide support for the power grid when operating on the grid and provide uninterrupted power supply to local critical loads when operating off the grid. It is a core technical challenge to ensure the power supply security and power quality of sensitive loads such as data centers and precision manufacturing when the converter is in the event of a grid failure.

[0003] A static transfer switch (STS) is a key device for achieving rapid isolation between the power grid and the converter, and is widely used in uninterruptible power supply (UPS) systems. It is typically composed of a bidirectional thyristor with low conduction losses and high overload capacity. The STS operates as follows: when the power grid is normal, the STS is on, and the grid directly supplies power to the load; when a voltage dip or interruption is detected, the STS must be quickly turned off, and the converter must be switched to off-grid mode to supply power to the load. However, as a semi-controlled device, the inherent characteristics of the thyristor mean it cannot be directly turned off by a gate control signal. It must wait for the current flowing through it to naturally cross zero. This waiting process can introduce an inherent delay of up to 10 milliseconds (half a cycle) in a power frequency (50Hz) system, resulting in a significant power interruption or voltage dip on the load side. This fails to meet the stringent requirements of high-end sensitive loads for seamless switching at millisecond or even sub-millisecond levels.

[0004] Therefore, there is an urgent need for a method that enables energy storage converters to achieve rapid STS shutdown and seamless off-grid switching in order to meet the power supply requirements of sensitive loads. Summary of the Invention

[0005] This invention provides a method for seamless switching of converters based on transient voltage injection (STS) for fast turn-off, in order to solve the problem of STS turn-off delay.

[0006] This invention provides a method for seamless switching of converters based on transient voltage injection (STS) fast turn-off, the method comprising: The electrical signals in the energy storage converter topology are acquired in real time, and a circuit model of the energy storage converter is established based on the characteristics and topological connection relationship of STS and supercapacitor. Real-time monitoring of grid connection point voltage; when the grid connection point voltage is within the normal range, control the energy storage converter to enter grid-connected operation mode and stabilize the supercapacitor voltage through active power control strategy. When a grid fault is detected, an STS shutdown command is issued to switch the control mode of the energy storage converter to the STS forced switching mode. The energy storage converter injects a preset transient shutdown voltage into the load-side output capacitor. At the same time, combined with the feedforward control quantities of the load current and the grid connection point voltage, the switching drive signal of the energy storage converter is calculated and generated. Continuously monitor the grid current. When it is determined that the STS is completely shut down, switch the control mode of the energy storage converter to the off-grid operation mode. Based on the phase and frequency of the preset grid connection point voltage, establish a stable power supply voltage for the load. The grid recovery status is monitored in real time. If the grid returns to normal, the control mode of the energy storage converter is switched to the pre-synchronization mode to synchronize the phase and amplitude of the output voltage of the energy storage converter with the grid voltage. After synchronization is completed, the control mode of the energy storage converter is switched to the grid-connected operation mode.

[0007] This invention provides a seamless switching method for converters based on transient voltage injection STS fast turn-off. By injecting a designed transient turn-off voltage into the output terminal of the energy storage converter itself, a forced current component opposite to the original current direction is directly generated in the STS circuit, thereby actively and quickly canceling the STS current and causing it to turn off rapidly at zero crossing. At the same time, dual feedforward control of load current and grid connection point voltage is introduced to decouple the commutation process from system disturbances, further reducing the response time and realizing seamless switching between grid connection and off-grid operation of the energy storage converter.

[0008] In one optional implementation, when the grid connection point voltage is within the normal range, the energy storage converter is controlled to enter grid-connected operation mode, and the supercapacitor voltage is stabilized through an active power control strategy, including: The grid-following current source control method is adopted. The positive sequence component of the output current reference of the energy storage converter is adjusted by the supercapacitor voltage regulator ring. The positive sequence current reference values ​​of the d-axis and q-axis are calculated. Then, the positive sequence current reference values ​​of the d-axis and q-axis are converted into three-phase positive sequence current reference values ​​in the three-phase stationary coordinate system through coordinate transformation. The zero-sequence current reference value is obtained by adjusting the zero-sequence component of the output current reference of the energy storage converter through the DC equalizing ring. The three-phase positive sequence current reference value, the energy storage converter output current, and the zero sequence current reference value are superimposed to obtain the total output current reference value in the three-phase stationary coordinate system. The total output current reference value is controlled in a closed loop using a proportional resonant current loop in the three-phase stationary coordinate system. At the same time, the grid connection point voltage feedforward is introduced to correct the control output, generating a modulation wave of the bidirectional DC / AC converter in the energy storage converter. After sinusoidal pulse width modulation processing, the switching drive signal of the bidirectional DC / AC converter is obtained. The DC / DC boost converter in the energy storage converter is controlled by a voltage and current dual-loop control strategy to generate a DC / DC boost converter modulation wave. After sinusoidal pulse width modulation processing, the switching drive signal of the DC / DC boost converter is obtained. Based on the switching drive signals of the DC / AC converter and the DC / DC boost converter, the power devices of the energy storage converter are driven to operate, thereby achieving stable control of the supercapacitor voltage.

[0009] In one alternative implementation, the formula for calculating the d-axis positive sequence current reference value is as follows:

[0010] In the formula, i ref,d This is the reference value for the positive sequence current along the d-axis. G sc (s) is a supercapacitor voltage controller. v sc This is the voltage of the supercapacitor. v sc_ref This is the rated voltage of the supercapacitor. k ps and k is These are the proportional and integral coefficients of the supercapacitor voltage controller, respectively. s For the Laplace transform operator.

[0011] In one alternative implementation, the zero-sequence current reference value is calculated using the following formula:

[0012] In the formula, i n This is the zero-sequence current reference value. G n (s) is a DC voltage equalization controller. This is the DC bus voltage. This is the lower DC bus voltage. k pn and k in These are the proportional coefficient and integral coefficient of the DC voltage equalization controller, respectively.

[0013] In one alternative implementation, the control expression for the modulated wave of the bidirectional DC / AC converter is as follows:

[0014] In the formula, This is a modulated wave for a bidirectional DC / AC converter. G i (s) is a current loop controller. This is the reference value for the three-phase positive sequence current. For the energy storage converter output current, The voltage at the grid connection point. k pi This is the proportionality coefficient. k ri The resonance coefficient, ω b The bandwidth at the center frequency, ω 0 represents the fundamental angular frequency.

[0015] In one optional implementation, the control expression for the modulation wave of the DC / DC boost converter is:

[0016] In the formula, v out1 The modulated wave for the DC / DC boost converter G idc (s) is the DC bus voltage controller. i b_ref This is the reference value for DC current. i b This is the DC side current. k pd and k id These are the proportional and integral coefficients of the DC bus voltage controller, respectively.

[0017] In one optional implementation, a preset transient shutdown voltage is injected into the load-side output capacitor by the energy storage converter. Simultaneously, a switching drive signal for the energy storage converter is calculated and generated by combining the feedforward control quantities of the load current and the grid connection point voltage, including: The preset transient shutdown voltage is determined based on the grid current and phase correction function; The preset transient shutdown voltage is superimposed with the grid connection point voltage to obtain the voltage reference value of the load-side output capacitor; Based on the preset transient shutdown voltage and the load-side output capacitor voltage, combined with the feedforward compensation term of the load current, the reference value of the three-phase positive sequence current in the STS forced commutation mode is calculated by the voltage controller. The proportional resonant current loop control logic of the grid-connected operation mode is reused. The deviation between the three-phase positive sequence current reference value and the output current of the energy storage converter is adjusted in a closed loop by the proportional resonant controller to generate the modulation wave base signal of the bidirectional DC / AC converter. The modulated wave base signal is corrected by introducing a grid connection point voltage feedforward compensation term, and after sinusoidal pulse width modulation processing, the switching drive signal of the bidirectional DC / AC converter is obtained.

[0018] In one alternative implementation, the formula for calculating the three-phase positive sequence current reference value in STS forced commutation mode is as follows:

[0019] In the formula, G v (s) is a voltage controller. k pv and k iv These are the proportional coefficient and resonant coefficient of the voltage controller, respectively. v (abc) The preset transient shutdown voltage is used. The output capacitor voltage on the load side. This is the load current.

[0020] In one optional implementation, a stable supply voltage is established for the load based on the phase and frequency of a preset grid connection point voltage, including: Based on the phase and frequency of the preset grid connection point voltage, combined with the rated voltage amplitude of the power grid, the off-grid voltage reference value with the same amplitude and phase as the grid connection point voltage is calculated using the sinusoidal voltage generation formula. The preset grid connection point voltage phase and frequency are the grid voltage phase and frequency latched at the moment of grid fault. The difference between the load-side output capacitor voltage and the off-grid voltage reference value is calculated by the voltage controller to obtain the three-phase positive sequence current reference value. The three-phase positive sequence current reference value, the energy storage converter output current, and the zero sequence current reference value are superimposed to obtain the total output current reference value in the three-phase stationary coordinate system. The total output current reference value is controlled in the three-phase stationary coordinate system by a proportional resonant current loop. At the same time, the off-grid voltage reference value is introduced to correct the control output, generating the modulation wave of the bidirectional DC / AC converter in the energy storage converter. After sinusoidal pulse width modulation processing, the switching drive signal of the bidirectional DC / AC converter is obtained. Based on the switching drive signal of the bidirectional DC / AC converter, the power devices of the energy storage converter are driven to operate, thereby establishing a stable power supply voltage for the load.

[0021] In one optional implementation, the control mode of the energy storage converter is switched to a pre-synchronization mode to synchronize the phase and amplitude of the energy storage converter output voltage with the grid voltage, including: Through the phase synchronization loop, a voltage reference phase value is generated by adjusting the PI controller based on the error between the phase of the grid connection point voltage and the phase of the energy storage converter output voltage. Through the amplitude synchronization loop, a voltage reference amplitude is generated by adjusting the PI controller based on the error between the amplitude of the grid connection point voltage and the amplitude of the energy storage converter output voltage. A pre-synchronization voltage reference value is synthesized based on the voltage reference phase value and the voltage reference amplitude value, and the output voltage of the energy storage converter is controlled to gradually track the grid voltage according to the pre-synchronization voltage reference value.

[0022] In one alternative implementation, The formula for calculating the voltage reference phase value is as follows:

[0023] In the formula, ref This is the voltage reference phase value. G a (s) is a phase synchronization controller. k pa and k ia These are the proportional and integral coefficients of the phase synchronization controller, respectively. The phase of the grid connection point voltage, This is the output voltage of the energy storage converter; The formula for calculating the voltage reference amplitude is as follows:

[0024] In the formula, E ref This is the voltage reference amplitude. G m (s) is a phase synchronization controller. k pm and k im These are the proportional and integral coefficients of the amplitude synchronization controller, respectively. The magnitude of the voltage at the grid connection point. This represents the amplitude of the output voltage of the energy storage converter.

[0025] Secondly, the present invention provides a converter seamless switching device based on transient voltage injection (STS) fast turn-off, the device comprising: The model building module is used to collect electrical signals in the energy storage converter topology in real time, and to establish the energy storage converter circuit model based on the characteristics and topological connection relationship of STS and supercapacitor. The first operating module is used to monitor the grid connection point voltage in real time. When the grid connection point voltage is within the normal range, it controls the energy storage converter to enter the grid connection operation mode and stabilizes the supercapacitor voltage through the active power control strategy. The second operation module is used to issue an STS shutdown command when a grid fault is detected, switch the control mode of the energy storage converter to the STS forced switching mode, inject a preset transient shutdown voltage into the load-side output capacitor by the energy storage converter, and calculate and generate the switching drive signal of the energy storage converter by combining the feedforward control quantities of the load current and the grid connection point voltage. The third operation module is used to continuously monitor the grid current. When it is determined that the STS is completely shut down, the control mode of the energy storage converter is switched to the off-grid operation mode. Based on the phase and frequency of the preset grid connection point voltage, a stable power supply voltage is established for the load. The fourth operation module is used to detect the grid recovery status in real time. If the grid returns to normal, the control mode of the energy storage converter is switched to the pre-synchronization mode to synchronize the phase and amplitude of the output voltage of the energy storage converter with the grid voltage. After synchronization is completed, the control mode of the energy storage converter is switched to the grid-connected operation mode.

[0026] This invention provides a seamless switching device for converters based on transient voltage injection STS fast turn-off. By injecting a designed transient turn-off voltage into the output terminal of the energy storage converter itself, a forced current component opposite to the original current direction is directly generated in the STS circuit, thereby actively and quickly canceling the STS current and causing it to turn off rapidly at zero crossing. At the same time, dual feedforward control of load current and grid connection point voltage is introduced to decouple the commutation process from system disturbances, further reducing the response time and realizing seamless switching between grid connection and off-grid of the energy storage converter.

[0027] Thirdly, the present invention provides an electronic device, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the converter seamless switching method based on transient voltage injection STS fast shutdown described in the first aspect or any corresponding embodiment above.

[0028] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to execute the converter seamless switching method based on transient voltage injection STS fast shutdown as described in the first aspect or any corresponding embodiment above. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a flowchart illustrating a converter seamless switching method based on transient voltage injection STS fast turn-off according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the energy storage converter topology according to an embodiment of the present invention; Figure 3 This is a control logic block diagram of the grid-connected operation mode according to an embodiment of the present invention; Figure 4 This is a control logic block diagram of the STS forced commutation mode according to an embodiment of the present invention; Figure 5 This is a theoretical commutation time variation curve according to an embodiment of the present invention; Figure 6 This is a flowchart of the energy storage converter control algorithm according to an embodiment of the present invention; Figure 7 This is a control block diagram for off-grid operation mode according to an embodiment of the present invention; Figure 8 This is another off-grid operation mode control block diagram according to an embodiment of the present invention; Figure 9 This is a block diagram of the off-grid pre-synchronization mode output voltage reference control according to an embodiment of the present invention; Figure 10 This is a waveform diagram of the system switching from grid connection to off-grid operation under the grid transient condition according to an embodiment of the present invention; Figure 11 This is a waveform diagram of the system switching from off-grid to on-grid after the power grid has returned to normal according to an embodiment of the present invention; Figure 12 This is a structural block diagram of a converter seamless switching device based on transient voltage injection STS fast turn-off according to an embodiment of the present invention. Figure 13 This is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It is understood that before using the technical solutions disclosed in the various embodiments of the present invention, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in the present invention and their authorization should be obtained in accordance with relevant laws and regulations through appropriate means.

[0033] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0034] To shorten the turn-off time of STS (Synchronous Transmission System), various forced commutation schemes have been proposed in the existing technology. One scheme involves constructing a passive resonant circuit between the thyristor switch and the external power grid, and achieving forced commutation through LC oscillation. Although this scheme is simple to control and has a fast response, it adds extra hardware circuitry, which not only increases the size and cost of the equipment, but also increases the difficulty of equipment coordination control and reduces power density. Another scheme is to achieve grid-connected and off-grid switching of energy storage devices by integrating multi-module hardware. However, its description of the core technology path of "seamless switching" is vague and does not deeply address the inherent turn-off delay problem caused by the physical characteristics of STS devices. In application scenarios with high power supply continuity, it faces the challenge of simultaneously optimizing switching time and voltage quality.

[0035] Furthermore, while existing forced commutation software algorithms that do not employ external circuitry aim to shorten the STS turn-off time, they suffer from severe load-side voltage distortion during commutation. This transforms the switching interruption time into voltage quality degradation time, prolonging the transient process of load voltage recovery and failing to achieve truly seamless switching. The fundamental reason is that the dynamic current decay of the STS during commutation is severely coupled with load current fluctuations and grid voltage disturbances, lacking an effective decoupling control mechanism to ensure that the commutation process is both fast and undisturbed.

[0036] To address the aforementioned problems, this invention provides a seamless switching method for converters based on transient voltage injection (STS) for rapid turn-off, such as... Figure 1 As shown, it includes the following steps: Step S1: Real-time acquisition of electrical signals in the energy storage converter topology; establishment of an energy storage converter circuit model based on the characteristics and topological connection relationship of the STS and supercapacitor.

[0037] Specifically, the energy storage converter topology is as follows: Figure 2 As shown, the system includes a bidirectional DC / AC converter on the grid-connected side and a DC / DC boost converter on the DC side. The bidirectional DC / AC converter connects the grid connection point to the DC bus, and the DC / DC boost converter connects the DC bus to the supercapacitor on the energy storage side. A static transfer switch (STS) consisting of three anti-parallel thyristors is connected at the grid connection point. The output current of the energy storage converter in the energy storage converter topology is acquired in real time. i L1Grid current i g DC side current i b Supercapacitor voltage v sc Load current i load Load-side output capacitor voltage v c Grid connection point voltage v pcc DC bus voltage v dc A circuit model of an energy storage converter based on STS and supercapacitors is established to provide a precise mathematical basis for subsequent control strategies and ensure that the control algorithm can accurately reflect the real dynamic behavior of the system.

[0038] Step S2: Monitor the grid connection point voltage in real time. When the grid connection point voltage is within the normal range, control the energy storage converter to enter the grid connection operation mode and stabilize the supercapacitor voltage through the active power control strategy.

[0039] Specifically, real-time monitoring of grid connection point voltage. E pcc If the grid connection point voltage is different from the rated voltage E 0 satisfies 0.9 E 0< E pcc <1.1 E If the value is 0, the power grid is considered to be normal, and the energy storage converter enters the grid-connected operation mode. In this mode, the supercapacitor voltage is stabilized by using the supercapacitor voltage regulator ring of the grid-connected bidirectional DC / AC converter and the DC bus voltage regulator ring of the DC / DC boost converter on the DC side through active power control.

[0040] Step S3: When a grid fault is detected, an STS shutdown command is issued to switch the control mode of the energy storage converter to the STS forced switching mode. The energy storage converter injects a preset transient shutdown voltage into the output capacitor on the load side. At the same time, the switching drive signal of the energy storage converter is calculated and generated by combining the feedforward control quantities of the load current and the grid connection point voltage.

[0041] Specifically, when a grid fault is detected, an STS shutdown command is immediately issued, and the control mode of the energy storage converter is switched to the STS forced switching mode. The energy storage converter actively injects a designed transient shutdown voltage into the output capacitor on the load side. At the same time, a feedforward control term of load current and grid connection point voltage is introduced into the control loop of the grid-connected converter to calculate and generate a switching drive signal.

[0042] When a grid fault is detected, a shutdown command is immediately sent to the STS (Support Switching System), and the control mode of the energy storage converter is switched to the STS forced commutation mode. A pre-designed transient shutdown voltage is actively injected into the load-side output capacitor by the energy storage converter. Simultaneously, a dual feedforward control quantity of load current and grid connection point voltage is introduced into the control loop of the grid-connected bidirectional DC / AC converter. Based on this feedforward control quantity and the transient shutdown voltage reference value, the switching drive signal of the grid-connected bidirectional DC / AC converter is calculated and generated.

[0043] Step S4: Continuously monitor the grid current. When it is determined that the STS is completely turned off, switch the control mode of the energy storage converter to the off-grid operation mode. Based on the phase and frequency of the preset grid connection point voltage, establish a stable power supply voltage for the load.

[0044] Specifically, during the STS commutation process, the STS switch status is continuously monitored. If grid current is detected... i g The current is less than the current detection threshold for three consecutive clock cycles. i th If the STS is completely shut down, the energy storage converter will switch to off-grid operation mode to quickly establish a stable power supply voltage for the load.

[0045] Step S5: Real-time monitoring of grid recovery status. If the grid has returned to normal, i.e., the voltage at the grid connection point matches the rated voltage... E 0 satisfies 0.9 E 0< E pcc <1.1 E 0. Switch the control mode of the energy storage converter to the pre-synchronization mode to synchronize the phase and amplitude of the output voltage of the energy storage converter with the grid voltage. After synchronization is completed, switch the control mode of the energy storage converter to the grid-connected operation mode.

[0046] Specifically, after the system goes offline, it continuously monitors whether the grid has returned to normal. If the grid has returned, the energy storage converter enters the offline pre-synchronization mode. Through phase synchronization loops and amplitude synchronization loops, the phase and amplitude of the output voltage are adjusted respectively to ensure complete synchronization with the grid voltage. |E pcc - E c |< E th , |θ pcc - θ c |< θ th ,in E th The voltage synchronization error threshold. θ thThis is the phase synchronization error threshold. This represents the amplitude of the output voltage of the energy storage converter. After synchronization is complete, switch back to grid-connected operation mode.

[0047] This invention provides a seamless switching method for converters based on transient voltage injection STS fast turn-off. By injecting a designed transient turn-off voltage into the output terminal of the energy storage converter itself, a forced current component opposite to the original current direction is directly generated in the STS circuit, thereby actively and quickly canceling the STS current and causing it to turn off rapidly at zero crossing. At the same time, dual feedforward control of load current and grid connection point voltage is introduced to decouple the commutation process from system disturbances, further reducing the response time and realizing seamless switching between grid connection and off-grid operation of the energy storage converter.

[0048] In one optional implementation, when the grid connection point voltage is within the normal range, the energy storage converter is controlled to enter grid-connected operation mode, and the supercapacitor voltage is stabilized through an active power control strategy, including the following steps: Step S21: Using a grid-following current source control method, the positive sequence component of the output current reference of the energy storage converter is adjusted by the supercapacitor voltage regulator ring to calculate the positive sequence current reference values ​​of the d-axis and q-axis. Then, the positive sequence current reference values ​​of the d-axis and q-axis are converted into three-phase positive sequence current reference values ​​in the three-phase stationary coordinate system through coordinate transformation.

[0049] Step S22: Adjust the zero-sequence component of the energy storage converter output current reference through the DC equalization ring to obtain the zero-sequence current reference value.

[0050] Step S23: The three-phase positive sequence current reference value, the energy storage converter output current, and the zero sequence current reference value are superimposed to obtain the total output current reference value in the three-phase stationary coordinate system. The total output current reference value is controlled in a closed loop using a proportional resonant current loop in the three-phase stationary coordinate system. At the same time, the grid connection point voltage feedforward is introduced to correct the control output, generating the bidirectional DC / AC converter modulation wave in the energy storage converter. After sinusoidal pulse width modulation processing, the switching drive signal of the bidirectional DC / AC converter is obtained.

[0051] Step S24: The DC / DC boost converter in the energy storage converter is controlled by a voltage and current dual-loop control strategy to generate a DC / DC boost converter modulation wave. After sinusoidal pulse width modulation processing, the switching drive signal of the DC / DC boost converter is obtained.

[0052] Step S25: Drive the power devices of the energy storage converter to operate according to the switching drive signals of the DC / AC converter and the DC / DC boost converter, so as to achieve stable control of the supercapacitor voltage.

[0053] Specifically, the control logic block diagram for grid-connected operation mode is as follows: Figure 3As shown, in grid-connected operation mode, the energy storage converter adopts a grid-following current source control method. The overall control system consists of three parts: a supercapacitor voltage regulator loop, a DC voltage equalization loop, and a current loop. The supercapacitor voltage regulator loop achieves voltage regulation control by adjusting the positive-sequence component of the energy storage converter's output current reference. When the energy storage converter is operating in grid-connected mode, the supercapacitor on the energy storage side is charged to its rated voltage, and the d-axis positive-sequence current reference value is calculated. i ref,d The q-axis positive sequence current reference value is set to 0. The formula for calculating the d-axis positive sequence current reference value is as follows:

[0054] In the formula, i ref,d This is the reference value for the positive sequence current along the d-axis. G sc (s) is a supercapacitor voltage controller. v sc This is the voltage of the supercapacitor. v sc_ref This is the rated voltage of the supercapacitor. k ps and k is These are the proportional and integral coefficients of the supercapacitor voltage controller, respectively. s For the Laplace transform operator.

[0055] The DC equalizing ring maintains voltage balance between the upper and lower DC buses by adjusting the zero-sequence component of the current reference, and calculates the zero-sequence current reference value. i n The formula for calculating the zero-sequence current reference value is as follows:

[0056] In the formula, i n This is the zero-sequence current reference value. G n (s) is a DC voltage equalization controller. This is the DC bus voltage. This is the lower DC bus voltage. k pn and k in These are the proportional coefficient and integral coefficient of the DC voltage equalization controller, respectively.

[0057] Reference value of three-phase positive sequence current Energy storage converter output current and zero-sequence current reference value i nThe superposition serves as the current reference value for the energy storage converter in the stationary coordinate system. A proportional resonant (PR) controller is used in the stationary coordinate system to perform closed-loop control of the energy storage converter's output current, generating a modulation wave for the bidirectional DC / AC converter. Its control expression is as follows:

[0058] In the formula, This is a modulated wave for a bidirectional DC / AC converter. G i (s) is a current loop controller. This is the reference value for the three-phase positive sequence current. For the energy storage converter output current, The voltage at the grid connection point. k pi This is the proportionality coefficient. k ri The resonance coefficient, ω b The bandwidth at the center frequency, ω 0 represents the fundamental angular frequency.

[0059] Modulating the wave of the bidirectional DC / AC converter Input a sinusoidal pulse width modulator to obtain the switching drive signal for the bidirectional DC / AC converter.

[0060] In all operating modes, the DC / DC boost converter on the DC side, including the supercapacitor, achieves DC bus voltage stability through dual-loop voltage and current control. The DC current reference value... i b_ref The expression is:

[0061] In the formula, G vdc (s) is the DC bus voltage controller. v dc_ref For DC bus voltage reference, k pvd and k ivd These are the proportional and integral coefficients of the DC bus voltage controller, respectively.

[0062] The control expression for the modulation wave of the DC / DC boost converter is:

[0063] In the formula, v out1 The modulated wave for the DC / DC boost converter G idc (s) is the DC bus voltage controller. ib_ref This is the reference value for DC current. i b This is the DC side current. k pd and k id These are the proportional and integral coefficients of the DC bus voltage controller, respectively.

[0064] Modulate the DC / DC boost converter wave v out1 Input a sinusoidal pulse width modulator to obtain the switching drive signal for the DC / DC boost converter.

[0065] In one optional implementation, a preset transient shutdown voltage is injected into the load-side output capacitor by the energy storage converter. Simultaneously, a switching drive signal for the energy storage converter is calculated and generated by combining the feedforward control quantities of the load current and the grid connection point voltage. This includes the following steps: Step S31: Determine the preset transient shutdown voltage based on the grid current and phase correction function.

[0066] Step S32: The preset transient shutdown voltage is superimposed with the grid connection point voltage to obtain the voltage reference value of the load-side output capacitor.

[0067] Step S33: Based on the preset transient shutdown voltage and the load-side output capacitor voltage, and combined with the feedforward compensation term of the load current, the reference value of the three-phase positive sequence current in the STS forced commutation mode is calculated by the voltage controller.

[0068] Step S34: Reuse the proportional resonant current loop control logic of the grid-connected operation mode, and use the proportional resonant controller to perform closed-loop adjustment on the deviation between the three-phase positive sequence current reference value and the output current of the energy storage converter to generate the modulation wave base signal of the bidirectional DC / AC converter.

[0069] Step S35: The grid connection point voltage feedforward compensation term is introduced to correct the modulation wave base signal. After sinusoidal pulse width modulation processing, the switching drive signal of the bidirectional DC / AC converter is obtained.

[0070] Specifically, the control logic block diagram of the STS forced commutation mode is as follows: Figure 4 As shown, when the STS drive signal is disconnected and the STS is not yet fully turned off, the energy storage converter operates in STS forced commutation mode. The energy storage converter quickly terminates the STS freewheeling process through active transient voltage injection control, which includes dual feedforward of load current and grid connection point voltage. The actively injected transient voltage... v (abc) From grid current i g(abc) Once the function is determined, its specific expression can be written as:

[0071] In the formula, u Voltage injection factor, f ( i g ) is the phase correction function.

[0072] Based on the response characteristics of the energy storage converter, the phase correction function can be calculated. f ( i g The specific expression for ) is:

[0073] By calculating the theoretical commutation time of the energy storage converter and selecting a voltage injection factor that keeps the commutation time below 0.4 ms, the voltage injection factor can be calculated. u for:

[0074] The energy storage converter achieves decoupling of the STS commutation process from disturbances through dual feedforward control of load current and grid connection point voltage. Based on the proportional resonant current loop control logic of the grid-connected operation mode, and using the transient voltage obtained above... v (abc) The reference value of the three-phase positive sequence current in the STS forced commutation mode can be calculated. i ref(abc) The expression is:

[0075] In the formula, G v (s) is a voltage controller. k pv and k iv These are the proportional coefficient and resonant coefficient of the voltage controller, respectively. v (abc) The preset transient shutdown voltage is used. The output capacitor voltage on the load side. This is the load current.

[0076] By reusing the proportional resonant current loop control logic of the grid-connected operation mode and introducing feedforward control of the grid-connected point voltage, the modulation signal of the bidirectional DC / AC converter on the grid-connected side of the system under the STS forced commutation mode can be calculated.

[0077] Figure 5 The commutation time is given under different initial grid current values. tThe curves show the changes in current. From bottom to top in the figure, these represent the initial grid current per-unit values ​​at the start of commutation. The variation curves under conditions of 0.1, 0.3, 0.6, and 1.0. t With the per-unit value of grid voltage x It decreases as the voltage injection factor increases. u At a given time, the theoretical commutation time depends on the magnitude of the grid current; the larger the grid current, the longer the theoretical commutation time. Based on the commutation time requirements in the system design, the voltage injection factor can be obtained at this time. u The value of is taken. In this embodiment, is taken as . .

[0078] Traditional uninterruptible power supply (UPS) systems rely on the natural zero-crossing of the thyristor current in the static transfer switch (STS) to achieve turn-off, resulting in an inherent delay of up to 10 ms during the switching process, which can easily lead to power outages. This embodiment utilizes the energy storage converter's own control system to actively inject a precisely designed transient turn-off voltage into the load side, achieving active and rapid cancellation of the STS current. This transforms the STS turn-off process from "passively waiting for the current to cross zero" to "actively controlling and forcing the current to cross zero," effectively shortening the system's grid connection and off-grid switching time and significantly improving the power supply reliability of sensitive loads.

[0079] Existing forced commutation technologies typically require the addition of passive resonant circuits and other hardware external to the STS (Switching Transmission System). While this can shorten the turn-off time, it increases system size, cost, and the risk of failure. This embodiment achieves "software-based" forced commutation entirely through improved control algorithms. Without adding any extra power hardware circuitry or system complexity, it achieves a switching speed comparable to or even better than traditional external hardware solutions, while maintaining high system power density, economy, and operational reliability.

[0080] Other software algorithms that only optimize the smoothness of control after mode switching are insufficient to address the issue of STS commutation being susceptible to load and grid disturbances. This embodiment innovatively introduces dual feedforward control terms for load current and grid connection point voltage in forced commutation control, effectively decoupling the dynamic process of the STS commutation loop from random power fluctuations on the load side and voltage disturbances on the grid side. This decoupling control significantly accelerates the response speed of the STS current to actively injected transient voltages, ensuring the stability and reliability of the commutation process under different operating conditions and optimizing the dynamic performance of the entire switching transient process. Figure 6 This is a flowchart of the control algorithm for the energy storage converter.

[0081] In one optional implementation, a stable supply voltage is established for the load based on the phase and frequency of a preset grid connection point voltage, including the following steps: Step S41: Based on the phase and frequency of the preset grid connection point voltage, combined with the rated voltage amplitude of the power grid, the off-grid voltage reference value with the same amplitude and phase as the grid connection point voltage is calculated using the sinusoidal voltage generation formula. The preset phase and frequency of the grid connection point voltage are the grid voltage phase and frequency latched at the moment of grid fault.

[0082] Step S42: The difference between the output capacitor voltage on the load side and the off-grid voltage reference value is calculated by the voltage controller to obtain the three-phase positive sequence current reference value.

[0083] Step S43: The three-phase positive sequence current reference value, the energy storage converter output current, and the zero sequence current reference value are superimposed to obtain the total output current reference value in the three-phase stationary coordinate system. The total output current reference value is controlled in a closed loop using a proportional resonant current loop in the three-phase stationary coordinate system. At the same time, the off-grid voltage reference value is introduced to correct the control output, generating the modulation wave of the bidirectional DC / AC converter in the energy storage converter. After sinusoidal pulse width modulation processing, the switching drive signal of the bidirectional DC / AC converter is obtained.

[0084] Step S44: Based on the switching drive signal of the bidirectional DC / AC converter, drive the power devices of the energy storage converter to operate and establish a stable power supply voltage for the load.

[0085] Specifically, the control logic block diagram for off-grid operation mode is as follows: Figure 7 and Figure 8 As shown, when a grid fault signal is detected, the energy storage converter quickly latches the phase and frequency of the grid voltage at the instant of the fault. Through the voltage reference generation stage, it calculates an off-grid voltage reference value that is in phase and amplitude with the normal grid voltage. v c_ref(abc) Its expression is:

[0086] In the formula, 0 is the initial phase angle of a power grid fault. ω 0 is the grid latching frequency (fundamental angular frequency).

[0087] In terms of control strategy, the existing voltage and current dual closed-loop control structure under the STS forced commutation mode is reused, the load current feedforward term is removed, and the original grid-connected point voltage feedforward is replaced with off-grid voltage reference value feedforward. Through this optimized closed-loop control, the output voltage of the energy storage converter is precisely regulated to ensure stable and continuous power supply to the load side during off-grid operation.

[0088] In one optional implementation, the control mode of the energy storage converter is switched to a pre-synchronization mode to synchronize the phase and amplitude of the energy storage converter output voltage with the grid voltage, including the following steps: Step S51: Through the phase synchronization loop, a voltage reference phase value is generated by adjusting the PI controller based on the error between the phase of the grid connection point voltage and the phase of the energy storage converter output voltage.

[0089] Step S52: Through the amplitude synchronization loop, a voltage reference amplitude is generated by adjusting the PI controller based on the error between the amplitude of the grid connection point voltage and the amplitude of the energy storage converter output voltage.

[0090] Step S53: Based on the voltage reference phase value and the voltage reference amplitude, a pre-synchronization voltage reference value is synthesized, and the output voltage of the energy storage converter is controlled to gradually track the grid voltage according to the pre-synchronization voltage reference value.

[0091] Specifically, the control logic block diagram of the off-grid pre-synchronization mode is as follows: Figure 9 As shown, this off-grid pre-synchronization mode achieves precise synchronization between the grid voltage and the converter output voltage by adjusting the output voltage reference value of the energy storage converter in real time. Specifically, two independent closed loops, a phase synchronization loop and an amplitude synchronization loop, are used to generate the phase of the voltage reference, respectively. ref With amplitude E ref The expression for the phase synchronization loop is: The formula for calculating the voltage reference phase value is as follows:

[0092] In the formula, ref This is the voltage reference phase value. G a (s) is a phase synchronization controller. k pa and k ia These are the proportional and integral coefficients of the phase synchronization controller, respectively. The phase of the grid connection point voltage, This is the output voltage of the energy storage converter; The formula for calculating the voltage reference amplitude is as follows:

[0093] In the formula, E ref This is the voltage reference amplitude. G m (s) is a phase synchronization controller. k pm and k im These are the proportional and integral coefficients of the amplitude synchronization controller, respectively. The magnitude of the voltage at the grid connection point. This represents the amplitude of the output voltage of the energy storage converter.

[0094] In terms of control strategy, the existing voltage and current dual closed-loop control structure in off-grid operation mode is reused, based on the voltage reference phase generated above. ref With amplitude E ref The system precisely controls the output voltage of the energy storage converter, enabling the output voltage of the energy storage converter to gradually track the grid voltage, achieving complete synchronization of the phase and amplitude of the two. This effectively reduces the current surge during the grid-connected / off-grid switching process, ensuring a smooth and undisturbed switching process.

[0095] Figure 10 This is a waveform diagram showing the system switching from grid-connected to off-grid operation under grid transient conditions. During this time, the energy storage converter monitors the grid in real time. To the right of the black line, a grid transient occurs. When the energy storage converter detects a grid fault, it shuts off the STS drive signal and switches to STS forced commutation mode. The energy storage converter outputs capacitor voltage on the load side. v c Actively inject transient shutdown voltage to ensure v c While maintaining continuity, the grid current will be... i g It rapidly decreases to zero. During this process... t 1 represents the time point of the power grid fault, at which the voltage at the grid connection point is... v pcc A temporary landing occurred; t At time 2, the equipment detects a voltage dip, at which point the energy storage converter enables the proposed STS forced commutation control; t At time 3, the grid current i g When the voltage drops to zero, the STS is completely shut down, and the energy storage converter switches to off-grid operation mode to supply power to the load. t Point 4 represents the load voltage recovery time, at which point the load voltage returns to its rated operating condition. Experimental results show that when the proposed STS forced commutation control is enabled, the switching time of the energy storage converter is [not specified]. t s The time has been reduced to less than 4ms, greatly reducing the switching time and enabling STS fast shutdown.

[0096] Figure 11 This is a waveform diagram showing the switching of the energy storage converter from off-grid to grid-connected after the grid has returned to normal. To the left of the black line, during a grid fault, the STS (Static Switching System) is off, and the energy storage converter is in off-grid operation mode. To the right of the black line, after the grid has returned to normal, the energy storage converter operates in off-grid pre-synchronization mode, synchronizing the output capacitor voltage on the load side. v c With grid connection point voltage v pccThe right figure shows the transient waveform of the energy storage converter (within the dashed box in the left figure) as it switches from off-grid voltage source control mode to grid-connected current source control mode. t r This is the switching time for the energy storage converter to switch from off-grid to grid-connected when the STS is turned on. At this time, the output of the energy storage converter has been synchronized with the grid connection point voltage, and the energy storage converter enables the STS drive signal and switches to grid-connected operation mode.

[0097] This embodiment also provides a converter seamless switching device based on transient voltage injection (STS) fast turn-off. This device is used to implement the above embodiments and preferred embodiments, and details already described will not be repeated. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0098] This embodiment provides a converter seamless switching device based on transient voltage injection STS fast turn-off, such as... Figure 12 As shown, it includes: Model building module 101 is used to collect electrical signals in the energy storage converter topology in real time and establish an energy storage converter circuit model based on the characteristics and topological connection relationship of STS and supercapacitor.

[0099] The first operating module 102 is used to monitor the grid connection point voltage in real time. When the grid connection point voltage is within the normal range, it controls the energy storage converter to enter the grid connection operation mode and stabilizes the supercapacitor voltage through the active power control strategy.

[0100] The second operation module 103 is used to issue an STS shutdown command when a grid fault is detected, switch the control mode of the energy storage converter to the STS forced switching mode, inject a preset transient shutdown voltage into the load-side output capacitor by the energy storage converter, and calculate and generate the switching drive signal of the energy storage converter by combining the feedforward control quantities of the load current and the grid connection point voltage.

[0101] The third operation module 104 is used to continuously monitor the grid current. When it is determined that the STS is completely shut down, the control mode of the energy storage converter is switched to the off-grid operation mode. Based on the phase and frequency of the preset grid connection point voltage, a stable power supply voltage is established for the load.

[0102] The fourth operation module 105 is used to detect the grid recovery status in real time. If the grid returns to normal, the control mode of the energy storage converter is switched to the pre-synchronization mode to synchronize the phase and amplitude of the output voltage of the energy storage converter with the grid voltage. After synchronization is completed, the control mode of the energy storage converter is switched to the grid-connected operation mode.

[0103] The converter seamless switching device based on transient voltage injection STS fast turn-off provided in this embodiment of the invention can execute the converter seamless switching method based on transient voltage injection STS fast turn-off provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects for executing the method. Further functional descriptions of the above modules and units are the same as in the corresponding embodiments described above, and will not be repeated here.

[0104] This invention provides a seamless switching device for converters based on transient voltage injection STS fast turn-off. By injecting a designed transient turn-off voltage into the output terminal of the energy storage converter itself, a forced current component opposite to the original current direction is directly generated in the STS circuit, thereby actively and quickly canceling the STS current and causing it to turn off rapidly at zero crossing. At the same time, dual feedforward control of load current and grid connection point voltage is introduced to decouple the commutation process from system disturbances, further reducing the response time and realizing seamless switching between grid connection and off-grid of the energy storage converter.

[0105] Figure 13 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention.

[0106] The following is a detailed reference. Figure 13 The diagram illustrates a structural schematic suitable for implementing an electronic device according to embodiments of the present invention. The electronic device may include a processor (e.g., a central processing unit, a graphics processing unit, etc.) 1101, which can perform various appropriate actions and processes according to a program stored in read-only memory (ROM) 1102 or a program loaded from memory 1108 into random access memory (RAM) 1103. The RAM 1103 also stores various programs and data required for the operation of the electronic device. The processor 1101, ROM 1102, and RAM 1103 are interconnected via a bus 1104. An input / output (I / O) interface 1105 is also connected to the bus 1104.

[0107] Typically, the following devices can be connected to I / O interface 1105: input devices 1106 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, accelerometers, gyroscopes, etc.; output devices 1107 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; memory devices 1108 including, for example, magnetic tapes, hard disks, etc.; and communication devices 1109. Communication device 1109 allows electronic devices to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 13 Electronic devices with various devices are shown, but it should be understood that it is not required to implement or have all of the devices shown, and more or fewer devices may be implemented or have instead.

[0108] In particular, according to embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of the present invention include a computer program product comprising a computer program carried on a non-transitory computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication device 1109, or installed from memory 1108, or installed from ROM 1102. When the computer program is executed by processor 1101, it performs the functions defined in the seamless switching method for converters based on transient voltage injection STS fast shutdown according to embodiments of the present invention.

[0109] Figure 13 The electronic device shown is merely an example and should not be construed as limiting the functionality and scope of use of the embodiments of the present invention.

[0110] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that the computer, processor, microprocessor controller, or programmable hardware includes storage components capable of storing or receiving software or computer code. When the software or computer code is accessed and executed by the computer, processor, or hardware, the seamless switching method for converters based on transient voltage injection (STS) fast shutdown shown in the above embodiments is implemented.

[0111] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for seamless switching of a converter based on a fast transient state voltage injection (STS) fast turn-off, characterized by, The method includes: The electrical signals in the energy storage converter topology are acquired in real time, and a circuit model of the energy storage converter is established based on the characteristics and topological connection relationship of STS and supercapacitor. Real-time monitoring of grid connection point voltage; when the grid connection point voltage is within the normal range, control the energy storage converter to enter grid-connected operation mode and stabilize the supercapacitor voltage through active power control strategy. When a grid fault is detected, an STS shutdown command is issued to switch the control mode of the energy storage converter to the STS forced switching mode. The energy storage converter injects a preset transient shutdown voltage into the load-side output capacitor. At the same time, combined with the feedforward control quantities of the load current and the grid connection point voltage, the switching drive signal of the energy storage converter is calculated and generated. Continuously monitor the grid current. When it is determined that the STS is completely shut down, switch the control mode of the energy storage converter to the off-grid operation mode. Based on the phase and frequency of the preset grid connection point voltage, establish a stable power supply voltage for the load. The grid recovery status is monitored in real time. If the grid returns to normal, the control mode of the energy storage converter is switched to the pre-synchronization mode to synchronize the phase and amplitude of the output voltage of the energy storage converter with the grid voltage. After synchronization is completed, the control mode of the energy storage converter is switched to the grid-connected operation mode.

2. The seamless switching method for converters based on transient voltage injection STS fast turn-off as described in claim 1, characterized in that, When the grid connection point voltage is within the normal range, the energy storage converter is controlled to enter grid-connected operation mode, and the supercapacitor voltage is stabilized through active power control strategies, including: The grid-following current source control method is adopted. The positive sequence component of the output current reference of the energy storage converter is adjusted by the supercapacitor voltage regulator ring. The positive sequence current reference values ​​of the d-axis and q-axis are calculated. Then, the positive sequence current reference values ​​of the d-axis and q-axis are converted into three-phase positive sequence current reference values ​​in the three-phase stationary coordinate system through coordinate transformation. The zero-sequence current reference value is obtained by adjusting the zero-sequence component of the output current reference of the energy storage converter through the DC equalizing ring. The three-phase positive sequence current reference value, the energy storage converter output current, and the zero sequence current reference value are superimposed to obtain the total output current reference value in the three-phase stationary coordinate system. The total output current reference value is controlled in a closed loop using a proportional resonant current loop in the three-phase stationary coordinate system. At the same time, the grid connection point voltage feedforward is introduced to correct the control output, generating a modulation wave of the bidirectional DC / AC converter in the energy storage converter. After sinusoidal pulse width modulation processing, the switching drive signal of the bidirectional DC / AC converter is obtained. The DC / DC boost converter in the energy storage converter is controlled by a voltage and current dual-loop control strategy to generate a DC / DC boost converter modulation wave. After sinusoidal pulse width modulation processing, the switching drive signal of the DC / DC boost converter is obtained. Based on the switching drive signals of the DC / AC converter and the DC / DC boost converter, the power devices of the energy storage converter are driven to operate, thereby achieving stable control of the supercapacitor voltage.

3. The seamless switching method for converters based on transient voltage injection STS fast turn-off as described in claim 2, characterized in that, The formula for calculating the d-axis positive sequence current reference value is as follows: In the formula, i ref,d This is the reference value for the positive sequence current along the d-axis. G sc (s) is a supercapacitor voltage controller. v sc This is the voltage of the supercapacitor. v sc_ref This is the rated voltage of the supercapacitor. k ps and k is These are the proportional and integral coefficients of the supercapacitor voltage controller, respectively. s For the Laplace transform operator.

4. The seamless switching method for converters based on transient voltage injection STS fast turn-off according to claim 2, characterized in that, The formula for calculating the zero-sequence current reference value is as follows: In the formula, i n This is the zero-sequence current reference value. G n (s) is a DC voltage equalization controller. This is the DC bus voltage. This is the lower DC bus voltage. k pn and k in These are the proportional coefficient and integral coefficient of the DC voltage equalization controller, respectively.

5. The seamless switching method for converters based on transient voltage injection STS fast turn-off according to claim 2, characterized in that, The control expression for the modulation wave of the bidirectional DC / AC converter is as follows: In the formula, This is a modulated wave for a bidirectional DC / AC converter. G i (s) is a current loop controller. This is the reference value for the three-phase positive sequence current. For the energy storage converter output current, The voltage at the grid connection point. k pi This is the proportionality coefficient. k ri The resonance coefficient, ω b The bandwidth at the center frequency, ω 0 represents the fundamental angular frequency.

6. The seamless switching method for converters based on transient voltage injection STS fast turn-off according to claim 2, characterized in that, The control expression for the modulation wave of the DC / DC boost converter is: In the formula, v out1 The modulated wave for the DC / DC boost converter G idc (s) is the DC bus voltage controller. i b_ref This is the reference value for DC current. i b This is the DC side current. k pd and k id These are the proportional and integral coefficients of the DC bus voltage controller, respectively.

7. The seamless switching method for converters based on transient voltage injection STS fast turn-off according to claim 2, characterized in that, A preset transient shutdown voltage is injected into the output capacitor on the load side by the energy storage converter. Simultaneously, combined with the feedforward control quantities of the load current and the grid connection point voltage, the switching drive signal for the energy storage converter is calculated and generated, including: The preset transient shutdown voltage is determined based on the grid current and phase correction function; The preset transient shutdown voltage is superimposed with the grid connection point voltage to obtain the voltage reference value of the load-side output capacitor; Based on the preset transient shutdown voltage and the load-side output capacitor voltage, combined with the feedforward compensation term of the load current, the reference value of the three-phase positive sequence current in the STS forced commutation mode is calculated by the voltage controller. The proportional resonant current loop control logic of the grid-connected operation mode is reused. The deviation between the three-phase positive sequence current reference value and the output current of the energy storage converter is adjusted in a closed loop by the proportional resonant controller to generate the modulation wave base signal of the bidirectional DC / AC converter. The modulated wave base signal is corrected by introducing a grid connection point voltage feedforward compensation term, and after sinusoidal pulse width modulation processing, the switching drive signal of the bidirectional DC / AC converter is obtained.

8. The seamless switching method for converters based on transient voltage injection STS fast turn-off according to claim 7, characterized in that, The formula for calculating the reference value of the three-phase positive sequence current in STS forced commutation mode is as follows: In the formula, G v (s) is a voltage controller. k pv and k iv These are the proportional coefficient and resonant coefficient of the voltage controller, respectively. v (abc) The preset transient shutdown voltage is used. The output capacitor voltage on the load side. This is the load current.

9. The seamless switching method for converters based on transient voltage injection STS fast turn-off according to claim 7, characterized in that, Based on the phase and frequency of the preset grid connection point voltage, a stable supply voltage is established for the load, including: Based on the phase and frequency of the preset grid connection point voltage, combined with the rated voltage amplitude of the power grid, the off-grid voltage reference value with the same amplitude and phase as the grid connection point voltage is calculated using the sinusoidal voltage generation formula. The preset grid connection point voltage phase and frequency are the grid voltage phase and frequency latched at the moment of grid fault. The difference between the load-side output capacitor voltage and the off-grid voltage reference value is calculated by the voltage controller to obtain the three-phase positive sequence current reference value. The three-phase positive sequence current reference value, the energy storage converter output current, and the zero sequence current reference value are superimposed to obtain the total output current reference value in the three-phase stationary coordinate system. The total output current reference value is controlled in the three-phase stationary coordinate system by a proportional resonant current loop. At the same time, the off-grid voltage reference value is introduced to correct the control output, generating the modulation wave of the bidirectional DC / AC converter in the energy storage converter. After sinusoidal pulse width modulation processing, the switching drive signal of the bidirectional DC / AC converter is obtained. Based on the switching drive signal of the bidirectional DC / AC converter, the power devices of the energy storage converter are driven to operate, thereby establishing a stable power supply voltage for the load.

10. The seamless switching method for converters based on transient voltage injection STS fast turn-off according to claim 1, characterized in that, Switch the control mode of the energy storage converter to pre-synchronization mode to synchronize the phase and amplitude of the energy storage converter output voltage with the grid voltage, including: Through the phase synchronization loop, a voltage reference phase value is generated by adjusting the PI controller based on the error between the phase of the grid connection point voltage and the phase of the energy storage converter output voltage. Through the amplitude synchronization loop, a voltage reference amplitude is generated by adjusting the PI controller based on the error between the amplitude of the grid connection point voltage and the amplitude of the energy storage converter output voltage. A pre-synchronization voltage reference value is synthesized based on the voltage reference phase value and the voltage reference amplitude value, and the output voltage of the energy storage converter is controlled to gradually track the grid voltage according to the pre-synchronization voltage reference value.

11. The seamless switching method for converters based on transient voltage injection STS fast turn-off according to claim 10, characterized in that, The formula for calculating the voltage reference phase value is as follows: In the formula, ref This is the voltage reference phase value. G a (s) is a phase synchronization controller. k pa and k ia These are the proportional and integral coefficients of the phase synchronization controller, respectively. The phase of the grid connection point voltage, This is the output voltage of the energy storage converter; The formula for calculating the voltage reference amplitude is as follows: In the formula, E ref This is the voltage reference amplitude. G m (s) is a phase synchronization controller. k pm and k im These are the proportional and integral coefficients of the amplitude synchronization controller, respectively. The magnitude of the voltage at the grid connection point. This represents the amplitude of the output voltage of the energy storage converter.

12. A seamless switching device for a converter based on transient voltage injection (STS) fast turn-off, characterized in that, The device includes: The model building module is used to collect electrical signals in the energy storage converter topology in real time, and to establish the energy storage converter circuit model based on the characteristics and topological connection relationship of STS and supercapacitor. The first operating module is used to monitor the grid connection point voltage in real time. When the grid connection point voltage is within the normal range, it controls the energy storage converter to enter the grid connection operation mode and stabilizes the supercapacitor voltage through the active power control strategy. The second operation module is used to issue an STS shutdown command when a grid fault is detected, switch the control mode of the energy storage converter to the STS forced switching mode, inject a preset transient shutdown voltage into the load-side output capacitor by the energy storage converter, and calculate and generate the switching drive signal of the energy storage converter by combining the feedforward control quantities of the load current and the grid connection point voltage. The third operation module is used to continuously monitor the grid current. When it is determined that the STS is completely shut down, the control mode of the energy storage converter is switched to the off-grid operation mode. Based on the phase and frequency of the preset grid connection point voltage, a stable power supply voltage is established for the load. The fourth operation module is used to detect the grid recovery status in real time. If the grid returns to normal, the control mode of the energy storage converter is switched to the pre-synchronization mode to synchronize the phase and amplitude of the output voltage of the energy storage converter with the grid voltage. After synchronization is completed, the control mode of the energy storage converter is switched to the grid-connected operation mode.

13. An electronic device, characterized in that, include: The system includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to perform the converter seamless switching method based on transient voltage injection (STS) fast shutdown as described in any one of claims 1 to 11.

14. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the converter seamless switching method based on transient voltage injection STS fast shutdown as described in any one of claims 1 to 11.

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