Resonance generator control method, controller and resonance generator

Abstract

The invention provides a control method of a resonance generator, a controller and the resonance generator, and relates to the technical field of electronic power. The resonance generator comprises a power supply, resonance equipment, impedance adjusting equipment and a controller which form a series resonance circuit; the resonance generator is used for being connected with to-be-tested equipment; the impedance adjusting device is composed of a cascaded H bridge, and the cascaded H bridge is composed of a plurality of H bridge modules; each H-bridge module comprises an H-bridge sub-module composed of four switch elements and a capacitor connected in parallel with the H-bridge sub-module; the method comprises the following steps: acquiring real-time resonance current of a resonance generator and capacitance voltage of an impedance adjusting device; inputting the real-time resonance current and the capacitor voltage into a control loop to obtain a modulation wave signal control quantity; and adjusting the impedance of the impedance adjusting device based on the modulated wave signal control quantity. According to the resonance generator provided by the invention, on the basis of light weight, continuous impedance adjustment of the impedance adjusting device is realized through the control loop.

Description

Technical Field

[0001] This invention relates to the field of electronic power technology, and in particular to a control method, controller and resonant generator for a resonant generator. Background Technology

[0002] With the continuous development and upgrading of power systems, the widespread application of flexible transmission and distribution technology, and the gradual implementation of complex power grid structures, modern new power systems are rapidly evolving towards larger scale, more complex topologies, and more diversified dynamic behaviors. Against the backdrop of building a new power system primarily based on new energy sources, to further enhance the monitoring and protection capabilities of power systems and accurately detect, locate, and repair various faults, pre-commissioning vector checks and equipment withstand voltage tests have been widely applied in the power generation, transmission, and conversion stages of power systems, covering core scenarios such as power plants and substations.

[0003] Vector inspection is an indispensable and crucial component in the construction and initial operation of various power plants, distribution stations, and substations, as well as in routine operation and maintenance. Its core function is to ensure the correct and reliable operation of secondary equipment, especially relay protection equipment, and to prevent power system safety risks caused by abnormal equipment coordination. As a vital technical support in the power system field, vector inspection technology and its related devices demonstrate irreplaceable application value in multiple key scenarios, including state estimation and online monitoring, electromagnetic transient recording and precise measurement, and relay protection device testing and commissioning, providing important guarantees for the safe and stable operation of new power systems.

[0004] In the practical application of vector testing devices, a high-amplitude sinusoidal quantity needs to be injected into the system as excitation. Taking sinusoidal current excitation as an example, a large excitation source and passive device are often required to meet the amplitude and phase requirements of the current. During secondary circuit vector testing, an AC power supply, a power capacitor, and a power inductor are connected in series to form a series resonant circuit to generate an excitation quantity with the required amplitude. The principle is to tune the large-capacity capacitor and inductor to a resonant state, using resonance to increase the current in the circuit to the required amplitude, which is then injected into the system under test to complete the vector test. Because large-capacity inductors contain components such as iron cores and windings, their weight and volume are enormous and increase with the inductor's capacity and inductance. This requires significant manpower and resources for transportation during testing, reducing the efficiency of the testing process. In addition, due to the complex and varied structures of various systems under test, their parameters are highly variable and heterogeneous. Vector checking requires reactors to have adjustable capabilities. However, current mainstream adjustable inductors mostly use tap-connectors or transformer-type impedance regulation. Tap-connectors offer poor continuity of inductance adjustment and are bulky; while transformer-type impedance regulation achieves continuous adjustment, the presence of primary and secondary windings still results in significant winding and core weight / volume, and the adjustment range is limited, hindering miniaturization and weight reduction. These problems significantly restrict the application and development of vector checking technology in power systems, posing challenges to the construction and optimization of new power systems. Summary of the Invention

[0005] This invention provides a control method, controller, and resonant generator for a resonant generator, to solve the problem that current resonant current generators cannot simultaneously achieve continuous impedance adjustment and ease of use.

[0006] In a first aspect, embodiments of the present invention provide a control method for a resonant generator, the resonant generator including a power supply forming a series resonant circuit, a resonant device, an impedance adjustment device, and a controller; the resonant generator is used to connect to a device under test; the impedance adjustment device is composed of cascaded H-bridges, the cascaded H-bridges being composed of multiple H-bridge modules; each H-bridge module includes an H-bridge sub-module composed of four switching elements, and a capacitor connected in parallel with the H-bridge sub-module; the method includes: Collect the real-time resonant current of the resonant generator and the capacitor voltage of the impedance adjustment device; The real-time resonant current and capacitor voltage are input into the control loop to obtain the modulated wave signal control quantity; The impedance of the impedance adjustment device is adjusted based on the control quantity of the modulation wave signal.

[0007] In an optional embodiment, the control loop includes a current loop and a phase loop; the modulation signal control quantity includes the amplitude control quantity and phase offset quantity of the modulation signal; the real-time resonant current and capacitor voltage are input into the control loop to obtain the modulation signal control quantity, including: The real-time resonant current is input into the current loop to obtain the amplitude control quantity; The capacitor voltage is input into the phase loop to obtain the phase offset.

[0008] In an optional embodiment, the real-time resonant current is input into the current loop to obtain an amplitude control quantity, including: Calculate the root mean square value of the real-time resonant current; Calculate the current difference between the root mean square value and the resonant current reference value; Calculate the adjustment amplitude based on the current difference; The amplitude of the adjustment is limited to obtain the amplitude control value.

[0009] In an optional embodiment, the capacitor voltage is the capacitor voltage of each H-bridge module in the impedance adjustment device; the capacitor voltage is input into the phase loop to obtain the phase offset, including: Calculate the phase of the resonant current based on the real-time resonant current; The DC capacitor voltage is obtained by averaging the capacitor voltages of each H-bridge module in the impedance adjustment device. Calculate the voltage difference between the DC capacitor voltage and the voltage reference value; Calculate the phase setpoint based on the voltage difference; The sum of the phase setpoint, the resonant current phase, and the preset phase compensation amount is used as the phase offset.

[0010] In an optional embodiment, adjusting the impedance of the impedance adjustment device based on the modulation wave signal control quantity includes: The control quantity of the modulated wave signal is modulated to obtain the driving signal; The switching elements in the cascaded H-bridge within the impedance regulation device are driven by a drive signal to adjust the impedance of the impedance regulation device.

[0011] In an optional embodiment, the method further includes: Soft-start control of the resonant generator; Accordingly, soft-start control of the resonant generator includes: The soft-start initial stage occurs when the real-time resonant current is less than the first preset threshold; the steady current ramp-up stage occurs when the real-time resonant current is not less than the first preset threshold and is less than the second preset threshold; and the steady-state operation stage occurs when the real-time resonant current is not less than the second preset threshold. In the initial stage of soft start, the auxiliary power supply of the impedance regulating device outputs a first preset voltage to provide power, so that the series resonant circuit operates with a first preset resonant current for a first preset time. After the first preset time, the output voltage of the auxiliary power supply of the impedance regulating device is gradually increased based on the preset voltage interval. When the output voltage of the auxiliary power supply of the impedance regulating device reaches the rated voltage, it enters the steady current ramp-up stage. During the steady current ramp-up phase, based on the preset resonant current interval, the resonant current setpoint of the series resonant circuit is gradually increased until the real-time resonant current reaches the resonant current reference value, and then the steady-state operation phase begins. During steady-state operation, the real-time resonant current and capacitor voltage are input into the control loop to obtain the modulation wave signal control quantity; and the impedance is adjusted based on the modulation wave signal control quantity.

[0012] In an optional embodiment, the method further includes: Implement soft-shutdown control for the resonant generator; Accordingly, soft-shutdown control of the resonant generator includes: Based on a preset voltage interval, the voltage reference value is reduced, causing the capacitor voltage to drop; After the capacitor voltage reaches the preset safe voltage threshold, the reference value of the resonant current is reduced based on the preset resonant current interval; After the real-time resonant current drops to 0, the current voltage reference value is reduced based on a preset voltage interval, and the resonant generator is shut down after the capacitor voltage drops to 0.

[0013] In a second aspect, embodiments of the present invention provide a controller, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method described in the first aspect or any possible implementation thereof.

[0014] Thirdly, embodiments of the present invention provide a resonant generator, including a power supply forming a series resonant circuit, a resonant device, an impedance adjustment device, and a controller as provided in the second aspect; the resonant generator is used to connect to a device under test. The impedance adjustment device consists of cascaded H-bridges, which are composed of multiple H-bridge modules. Each H-bridge module includes an H-bridge sub-module consisting of four switching elements and a capacitor connected in parallel with the H-bridge sub-module.

[0015] In an optional embodiment, when the resonant generator is connected in series with the device under test (DUT), the resonant generator is used to perform vector detection on the DUT; when the resonant generator is connected in parallel with the DUT, the resonant generator is used to perform withstand voltage testing on the DUT; wherein, when the resonant generator is connected in parallel with the DUT, the DUT is connected in parallel across the two ends of the resonant generator.

[0016] In this embodiment of the invention, an impedance control device composed of cascaded H-bridges is used to form a series resonant circuit with the power supply and resonant equipment to obtain a resonant generator. Replacing traditional large-capacity inductors and transformer-type impedance devices with cascaded H-bridges, which do not include iron cores, windings, or other components, results in smaller size, lighter weight, and easier portability, thus improving the effectiveness of testing experiments. Traditional tap-type adjustments essentially mechanically change the number of winding turns. The tap switches the number of winding turns connected via mechanical contacts, and each switch only yields a fixed inductive reactance value for the corresponding number of turns, resulting in discrete inductive reactance step values ​​and failing to achieve stepless adjustment. In contrast, this embodiment uses a cascaded H-bridge topology, which includes an H-bridge submodule composed of switching elements and a capacitor. By driving the high-frequency switching of the switching elements of the cascaded H-bridge, the capacitance of the impedance adjustment device changes, achieving continuous adjustment of the modulated wave signal and thus continuously changing the equivalent impedance properties and impedance value of the cascaded H-bridge. The impedance adjustment device adjusts the impedance in the resonant generator to adjust the magnitude of the resonant current, enabling the resonant generator to provide the target resonant current to the device under test. This adjustment process is based on the digital modulation of electrical signals, requiring no mechanical structure. Furthermore, it responds to deviation signals in real time through closed-loop control, allowing the equivalent impedance to smoothly transition within a set range. This ultimately achieves continuous and precise impedance adjustment, overcoming the discrete limitations of traditional tap-type adjustments. Therefore, the resonant generator provided in this embodiment of the invention can achieve continuous impedance adjustment of the impedance adjustment device through a corresponding control loop while maintaining a lightweight design, thereby realizing resonance adjustment and the amplification and generation of voltage and current in the resonant circuit. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a traditional resonant regulation circuit based on a mechanically adjustable reactor; Figure 2 This is a topology diagram of the resonant generator provided in an embodiment of the present invention; Figure 3 This is a diagram of the resonant generator connected to a three-phase Y-connected system architecture provided in an embodiment of the present invention; Figure 4 This is a diagram of the three-phase delta-connected resonant generator system architecture provided in an embodiment of the present invention; Figure 5 This is a diagram illustrating the extension of the resonant generator provided in this embodiment of the invention to include an isolation transformer; Figure 6 This is a topology diagram of the resonant generator provided in the embodiment of the present invention used for withstand voltage testing; Figure 7 This is a flowchart illustrating the implementation of the control method for the resonant generator provided in this embodiment of the invention; Figure 8This refers to the control loop in the resonant generator provided in the embodiments of the present invention; Figure 9 This is a current waveform diagram of the resonant generator provided in the embodiment of the present invention during the soft-start process; Figure 10 This is an AC voltage waveform diagram across the impedance adjustment device of the resonant generator provided in the embodiment of the present invention during the soft-start process; Figure 11a This is the waveform diagram of the capacitor voltage in phase A; Figure 11b This is the waveform diagram of the voltage across phase B capacitor; Figure 11c This is a waveform diagram of the voltage across phase C capacitor; Figure 12 This is a schematic diagram of the controller provided in an embodiment of the present invention. Detailed Implementation

[0018] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] Figure 1 This is a schematic diagram of a traditional resonant regulation circuit based on a mechanically adjustable reactor, such as... Figure 1 As shown, a traditional resonant regulation circuit based on a mechanically adjustable reactor includes a power supply, a power capacitor, and a power inductor. However, traditional power inductor devices contain components such as iron cores and windings, resulting in a large weight and volume that increases with the inductor's capacity and inductance. This necessitates significant manpower and resources for transportation during testing, reducing testing efficiency. Furthermore, when using tap-connectors for adjustment, the continuity of inductance adjustment is poor, and the device remains bulky. While transformer-type impedance regulation allows for controllable adjustment of the equivalent input on the secondary side, thereby changing the equivalent impedance of the primary side port in the circuit, achieving continuous adjustment, the presence of the primary and secondary side structures still results in a large weight / volume of the required windings and iron core, and the adjustment range is limited, hindering miniaturization and weight reduction.

[0020] To address these issues, embodiments of the present invention provide a novel resonant generator, the topology of which is as follows: Figure 2 As shown.

[0021] The resonant generator provided in this embodiment of the invention uses an impedance adjustment device instead of a traditional power inductor device. Specifically, the resonant current generator includes a power supply forming a series resonant circuit, a resonant device, an impedance adjustment device, and a controller; the resonant generator is used to connect to the device under test; wherein, the power supply can be a low-voltage AC power supply; the resonant device can be a capacitor or a resistor; the impedance adjustment device is composed of a cascaded H-bridge (CHB), which is composed of multiple H-bridge modules; each H-bridge module includes an H-bridge sub-module composed of four switching elements, and a capacitor connected in parallel with the H-bridge sub-module.

[0022] For any given H-bridge module, the four switching elements are designated S1, S2, S3, and S4 along their instantaneous values. When the H-bridge module is operating normally, the drive signals of S1, S2, S3, and S4 on the same path are interlocked, preventing them from being triggered simultaneously. When the H-bridge module malfunctions or its DC capacitor experiences prolonged overvoltage or undervoltage, switching transistors 1 and 4 (or 2 and 3) will be triggered, causing the submodule to be bypassed and enter a fault maintenance state.

[0023] By replacing traditional large-capacity inductor and transformer-type impedance devices with cascaded H-bridges, which do not contain iron cores, windings, or other components, the devices are small in size, lightweight, and easy to move, thus improving the effectiveness of testing experiments.

[0024] The reactance in the resonant generator is determined by the sum of the line reactance and the reactance of the impedance adjustment device. Since the line reactance is a fixed value, this embodiment achieves adjustable impedance of the resonant generator by adjusting the impedance of the impedance adjustment device. Specifically, during the adjustment process, the impedance adjustment device works in conjunction with the control logic in the controller to adjust the magnitude of the resonant current by adjusting the impedance in the resonant generator, so that the resonant generator provides the target resonant current to the device under test.

[0025] Figure 2 The provided resonant generator is a schematic diagram of a unidirectional topology. In addition to being used in single-phase lines, the resonant generator provided in this embodiment of the invention can also be used in multi-phase lines. In multi-phase lines, the number of resonant generators is determined according to the number of phases.

[0026] Figure 3 and Figure 4 These are, respectively, the architecture diagrams of the resonant generator connected to a three-phase Y-connected system and the three-phase delta-connected system provided in the embodiments of the present invention.

[0027] In other words, the resonant generator provided in this embodiment can be combined to obtain a three-phase topology, which can be applied to various systems, such as CT systems in vector inspection, three-phase transformers in withstand voltage tests, three-phase circuit breakers, and other equipment. It can be connected to three-phase three-wire systems, three-phase four-wire systems, single-phase systems, grounded / ungrounded systems, or grounded systems through arc suppression coils.

[0028] Figure 5 This is a diagram illustrating the extension of the resonant generator provided in this embodiment of the invention to include an isolation transformer, as shown below. Figure 5 As shown.

[0029] Figure 2 The impedance adjustment device provided is a direct-connect CHB type. To achieve electrical isolation and improve safety, the impedance adjustment device can be improved to include an isolation transformer, i.e., an isolation transformer is connected in parallel with the cascaded H-bridge. However, introducing this isolation transformer will increase the overall size and weight of the device. The specific form of the impedance adjustment device can be adjusted according to the actual needs of the application.

[0030] In an optional embodiment, to ensure mature control and high overall reliability, the pressure resistance of the valve group can be improved by increasing the number of stages, that is, increasing the number of sub-H-bridge modules in the CHB. The CHB adopts a redundant design, mature control, and high reliability. When a cascaded module fails, the backup module can be quickly bypassed and activated, thereby improving the overall reliability.

[0031] Figure 2 The diagram shown illustrates the topology of a resonant generator used for vector detection. During vector detection, the resonant generator is connected in series with the device under test (DUT), which is specifically connected in series after an impedance adjustment device. In this case, the resonant generator functions as a resonant current generator, used to adjust the resonant current input to the DUT.

[0032] In addition to being used for vector detection, this resonant generator can also be used for withstand voltage testing. Figure 6 This is a topology diagram of the resonant generator provided in the embodiments of the present invention used for withstand voltage testing; as shown. Figure 6 As shown, during the withstand voltage test, the resonant generator is connected in parallel with the device under test (DUT). Specifically, the DUT is connected in parallel across the two ends of the resonant generator. In this case, the resonant generator acts as a resonant voltage generator, used to adjust the resonant voltage input to the DUT.

[0033] When performing vector detection and withstand voltage testing, the controller of this resonant generator executes the same control logic, which is: Figure 7 The control method for the provided resonant generator, such as Figure 7 As shown, the method includes: Step 110: Collect the real-time resonant current of the resonant generator and the capacitor voltage of the impedance adjustment device.

[0034] The real-time resonant current of the resonant generator is the total current in the series resonant circuit. The capacitor voltage of the impedance adjustment device is the capacitor voltage of each H-bridge module.

[0035] Step 120: Input the real-time resonant current and capacitor voltage into the control loop to obtain the modulated wave signal control quantity.

[0036] Figure 8 This refers to the control loop in the resonant generator provided in the embodiments of the present invention; such as Figure 8 As shown, the control loop includes a current loop and a phase loop; correspondingly, the modulation signal control quantities include the amplitude control quantity and the phase offset quantity of the modulation signal.

[0037] The real-time resonant current is input into the current loop to obtain the amplitude control value. The capacitor voltage is input into the phase loop to obtain the phase offset value.

[0038] The above method enables precise tracking of the target value by the resonant current, with continuous and smooth adjustment to meet experimental accuracy requirements. It also allows for rapid control response, adaptability to different experimental scenarios and system wiring, and enhances the versatility and reliability of the device.

[0039] Step 130: Adjust the impedance of the impedance adjustment device based on the modulation wave signal control quantity.

[0040] In this embodiment, the modulated wave signal control quantity is used to perform feedforward control on the impedance of the impedance adjustment device. By modulating the modulated wave signal control quantity, it is used to drive each cascaded H-bridge to conduct accordingly, thereby adjusting the impedance of the impedance adjustment device. Through impedance adjustment, the real-time resonant current of the resonant generator can be feedforward adjusted, changing the magnitude of the total impedance in the resonant generator to amplify or reduce it to meet the target resonant current or target resonant voltage required for testing.

[0041] In summary, this invention improves the resonant generator by replacing the traditional mechanical adjustable inductor with a cascaded H-bridge. Furthermore, through software logic, the impedance of the cascaded H-bridge is adjusted, changing the total impedance of the resonant generator to amplify or reduce it to meet the target resonant current required for testing. This method, combining software control and hardware improvements, enables continuous impedance adjustment of the impedance regulating device through appropriate control loops while achieving a lightweight design.

[0042] The relevant control logic of the control loop is explained below through the following related examples: In an optional embodiment, the real-time resonant current is input into the current loop to obtain an amplitude control quantity, including: Calculate the root mean square (RMS) value of the real-time resonant current.

[0043] Calculate the current difference between the root mean square value and the resonant current reference value.

[0044] Calculate the adjustment amplitude based on the current difference.

[0045] The amplitude of the adjustment is limited to obtain the amplitude control value.

[0046] In this embodiment, the resonant current is acquired in real time, and its root mean square (RMS) value is calculated in real time. To reduce system complexity and prevent high-frequency interference, the RMS value is fed forward as a reference value into the current loop at each preset time interval.

[0047] In a current loop, calculate the root mean square value. I S With resonant current reference value I S_ref Current difference I S .

[0048] Current difference I S The input is fed into the PI controller to obtain the adjustment amplitude.

[0049] The modulation amplitude is limited, and amplitudes exceeding the limit are removed to obtain the modulation wave amplitude control value. u m * The modulation amplitude control value u m * Used to control the amplitude of the modulated wave.

[0050] In an optional embodiment, the capacitor voltage is the capacitor voltage of each H-bridge module in the impedance adjustment device, i.e., the capacitor voltage. V sm (i); Input the capacitor voltage into the phase loop to obtain the phase offset, including: Calculate the phase of the resonant current based on the real-time resonant current.

[0051] The DC capacitor voltage is obtained by averaging the capacitor voltages of each H-bridge module in the impedance adjustment device.

[0052] Calculate the voltage difference between the DC capacitor voltage and the voltage reference value.

[0053] Calculate the phase setpoint based on the voltage difference.

[0054] The sum of the phase setpoint, the resonant current phase, and the preset phase compensation amount is used as the phase offset.

[0055] The DC capacitor voltage is calculated using the following formula:

[0056] In the formula, V DC This is the DC capacitor voltage; V sm (i) represents the capacitor voltage of each H-bridge module; n represents the number of H-bridge modules.

[0057] In this embodiment, the phase of the resonant current is calculated based on the real-time resonant current. θ i .

[0058] DC capacitor voltage V DC With voltage reference value V dc_ref The input is fed into the phase loop, and the voltage difference is obtained after subtraction. V DC and the voltage difference V DC The input is a PI circuit, and the modulated wave phase setpoint is obtained after proportional-integral calculation and amplitude limiting by the PI circuit. θ *

[0059] Phase given value θ * Resonant current phase θ i and preset phase compensation amount θ m The phase shift is obtained by summing. θ, to adjust the modulated wave u m The phase offset.

[0060] In an optional embodiment, the method further includes: Soft-start control is applied to the resonant generator.

[0061] Accordingly, soft-start control of the resonant generator includes: The soft-start initial stage occurs when the real-time resonant current is less than the first preset threshold; the steady current ramp-up stage occurs when the real-time resonant current is not less than the first preset threshold and is less than the second preset threshold; and the steady-state operation stage occurs when the real-time resonant current is not less than the second preset threshold.

[0062] In the initial stage of soft start, the auxiliary power supply of the impedance regulating device outputs a first preset voltage to provide power, so that the series resonant circuit operates with a first preset resonant current for a first preset time. After the first preset time, the output voltage of the auxiliary power supply of the impedance regulating device is gradually increased based on the preset voltage interval. When the output voltage of the auxiliary power supply of the impedance regulating device reaches the rated voltage, it enters the steady current ramp-up stage.

[0063] During the steady current ramp-up phase, based on the preset resonant current interval, the resonant current setpoint of the series resonant circuit is gradually increased until the real-time resonant current reaches the resonant current reference value, at which point the system enters the steady-state operation phase.

[0064] During steady-state operation, the real-time resonant current and capacitor voltage are input into the control loop to obtain the modulation wave signal control quantity; and the impedance is adjusted based on the modulation wave signal control quantity.

[0065] To ensure that the capacitor does not overcharge during the startup of the resonant generator and to guarantee the safety of the components, the embodiments of the present invention provide the above soft-start strategy.

[0066] This embodiment divides the entire soft-start process into three stages based on the real-time resonant current value during the soft-start process: the initial stage of soft-start, the steady current increase stage, and the steady-state operation stage.

[0067] During the initial soft-start phase, power is supplied by the auxiliary power supply of the cascaded H-bridge. At this time, the same-side switching elements in all H-bridge modules are turned on; for example, S1 and S2 are turned on simultaneously, or S3 and S4 are turned on simultaneously. The voltage output by the auxiliary power supply at this time... U S Independently driven resonant device C r * and the device under test L dtu At this point, the circuit is in free resonance, and the resonant current is jointly determined by the auxiliary power supply, the resonant device, and the device under test. The output voltage of the auxiliary power supply is maintained at a small initial value, and the resonant current is also small, in order to start the resonant generator. Within a first preset time, all H-bridge modules are engaged, and the series resonant circuit operates at a first preset resonant current, which is determined in the following way:

[0068] After a first preset time, the output voltage of the auxiliary power supply of the impedance regulating device is gradually increased based on a preset voltage interval until the output voltage of the auxiliary power supply of the impedance regulating device reaches the rated voltage. In this device, the voltage across the capacitors in each H-bridge module is maintained at a small initial value, ensuring that the control loop of the H-bridge module is energized. Then, the control loop starts to operate to control phase shifting or cascaded PWM waveform generation, enabling it to regulate impedance.

[0069] During the steady current ramp-up phase, based on the preset resonant current interval, the real-time resonant current is gradually increased from a small initial value to the resonant current setpoint until the real-time resonant current reaches the resonant current reference value, at which point the system enters the steady-state operation phase. In this phase, the capacitors in each H-bridge module are gradually charged from a small initial value, and as the resonant current reference value increases, the total voltage across the cascaded H-bridges increases as the total impedance of the series resonant circuit decreases.

[0070] In this process, the rated voltage, i.e., the voltage reference value, is calculated based on the real-time changing resonant current reference value, and its calculation formula is as follows:

[0071] During the steady-state operation phase, the resonant generator is started up and put into use, and begins to execute steps 110 to 140.

[0072] Figure 9 This is a current waveform diagram of the resonant generator provided in this embodiment of the invention during the soft-start process; the horizontal axis represents time, and the vertical axis represents the current amplitude. As can be seen from the diagram, in the initial stage of startup, through the proposed soft-start strategy, the current smoothly rises from zero to the preset steady-state target value without overshoot, rather than experiencing the surge current that may be caused by traditional direct closing. This waveform demonstrates that the soft-start strategy adopted in this invention can effectively limit the starting current, avoid current surges to the power grid, internal power devices, and the device under test, and ensure a safe and controllable testing process.

[0073] Figure 10 This is an AC voltage waveform diagram across the impedance adjustment device of the resonant generator provided in this embodiment of the invention during the soft-start process; wherein, Figures 11a-11c Corresponding to Figure 10 The various electric voltages in the system.

[0074] exist Figure 10In the graph, the horizontal axis represents time, and the vertical axis represents voltage amplitude. This graph reflects that under soft-start control, the DC capacitor voltages of each H-bridge module are charged to their rated operating voltage in an orderly and stable manner, without voltage overshoot or imbalance. This result verifies the effectiveness of the soft-start strategy of this invention in avoiding capacitor overvoltage and ensuring voltage equalization among multiple modules, thus ensuring the safety of power electronic modules during startup and extending the service life of the equipment.

[0075] In an optional embodiment, the method further includes: Implement soft-shutdown control for the resonant generator.

[0076] Accordingly, soft-shutdown control of the resonant generator includes: Based on a preset voltage interval, the voltage reference value is reduced, causing the capacitor voltage to drop.

[0077] After the capacitor voltage reaches the preset safe voltage threshold, the reference value of the resonant current is reduced based on the preset resonant current interval.

[0078] After the real-time resonant current drops to 0, the current voltage reference value is reduced based on a preset voltage interval, and the resonant generator is shut down after the capacitor voltage drops to 0.

[0079] To control the safe disconnection of the resonant generator, ensure complete capacitor discharge during and after shutdown, and provide an electrically isolated topology connection to guarantee the safety of equipment and personnel, this embodiment also provides a soft shutdown control strategy.

[0080] This strategy can be applied when the instrument needs to be stopped, shut down, or repaired. When implementing this strategy, firstly, the resonant current reference value I is controlled. s_ref The voltage reference value V remains unchanged, and is gradually decreased based on a preset voltage interval. dc_ref This causes the capacitor voltage to gradually decrease. Once the capacitor voltage drops to the safe voltage threshold, the resonant current reference value is adjusted.

[0081] During the adjustment process, the current command value I can be adjusted based on a preset resonant current interval. s_ref The current drops to 0 in a stepwise manner; thereafter, the resonant circuit current is approximately equal to... U s / Z Cr* Then gradually adjust the current voltage reference value Us to 0, reduce the loop current to 0, and complete the shutdown.

[0082] In summary, firstly, the embodiments of this invention employ an impedance control device composed of cascaded H-bridges, forming a series resonant circuit with the power supply and resonant equipment to obtain a resonant generator. By replacing traditional large-capacity inductor devices and transformer-type impedance devices with cascaded H-bridges, which do not include components such as iron cores and windings, the device achieves small size, lightweight design, and ease of movement, thus improving the effectiveness of testing experiments. It avoids the problems of discontinuous adjustment and capacity waste caused by tap changes or transformer secondary capacity in traditional adjustable reactance devices, significantly improving the adjustment performance and energy efficiency of the resonant generator while ensuring flexible and controllable resonant current and voltage. Secondly, the resonant generator provided in these embodiments is expandable, compatible with various system wiring configurations such as Y-connection, Δ-connection, three-phase four-wire, and three-phase three-wire, with independent phase control for each phase, adapting to various field testing scenarios without complex external conversion equipment. Simultaneously, the CHB-based modulation strategy effectively suppresses output harmonics, avoiding the injection of harmonic interference into the system under test, and is compatible with the testing of relay protection equipment such as phase comparators, PTs, and CTs, improving the safety and reliability of the test. Furthermore, this embodiment designs a closed-loop strategy with resonant current and DC-side voltage as control targets. Combined with soft-start charging and shutdown discharge protection processes, it achieves stable and controllable operation and safe operation during device switching. This control method has a clear structure and strong robustness, maintaining precise stability of the resonant current over a wide range of impedance adjustments. Simultaneously, the proposed impedance calculation method balances simplicity and engineering accuracy, providing a reliable tool for impedance analysis of resonant circuit ports with PWM control, further enhancing the practicality and scalability of the entire system. Finally, the impedance control device provided in this embodiment, compared to a switched inductor-type adjustable reactor, has continuous current flowing through its two ends and no inherent inductance, further reducing device size. Moreover, it eliminates overvoltage problems caused by sudden changes in inductor current without the need for an additional freewheeling path, making it safer, more reliable, and with lower harmonic content.

[0083] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0084] Figure 12 This is a schematic diagram of the controller provided in an embodiment of the present invention. Figure 12 As shown, the controller 12 in this embodiment includes a processor 120 and a memory 121. The memory 121 stores a computer program 122. When the processor 120 executes the computer program 122, it implements the steps in the various method embodiments described above. Alternatively, when the processor 120 executes the computer program 122, it implements the functions of each module / unit in the various device embodiments described above.

[0085] For example, computer program 122 may be divided into one or more modules / units, which are stored in memory 121 and executed by processor 120 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 122 in controller 12.

[0086] The controller 12 may include, but is not limited to, a processor 120 and a memory 121. Those skilled in the art will understand that... Figure 12 This is merely an example of controller 12 and does not constitute a limitation on controller 12. It may include more or fewer components than shown, or combine certain components, or use different components.

[0087] For the sake of simplicity and clarity, only the above-described functional modules / units are used as examples. In practical applications, the functions described above can be assigned to different functional modules / units as needed. These modules / units can be implemented in hardware, software, or a combination of both.

[0088] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not detailed or described in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Unless otherwise specified or in conflict with logic, the terminology and / or descriptions between different embodiments are consistent and can be referenced interchangeably. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0089] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A control method for a resonant generator, characterized in that, The resonant generator includes a power supply forming a series resonant circuit, a resonant device, an impedance adjustment device, and a controller; the resonant generator is used to connect to the device under test; the impedance adjustment device consists of cascaded H-bridges, which are composed of multiple H-bridge modules; each H-bridge module includes an H-bridge sub-module consisting of four switching elements, and a capacitor connected in parallel with the H-bridge sub-module; the method includes: The real-time resonant current of the resonant generator and the capacitor voltage of the impedance adjustment device are collected. The real-time resonant current and the capacitor voltage are input into the control loop to obtain the modulated wave signal control quantity; The impedance of the impedance adjustment device is adjusted based on the modulation wave signal control quantity.

2. The control method for the resonant generator according to claim 1, characterized in that, The control loop includes a current loop and a phase loop; the modulation signal control quantity includes the amplitude control quantity and phase offset quantity of the modulation signal; the step of inputting the real-time resonant current and the capacitor voltage into the control loop to obtain the modulation signal control quantity includes: The real-time resonant current is input into the current loop to obtain the amplitude control quantity; The capacitor voltage is input into the phase loop to obtain the phase offset.

3. The control method for the resonant generator according to claim 2, characterized in that, The step of inputting the real-time resonant current into the current loop to obtain the amplitude control quantity includes: Calculate the root mean square value of the real-time resonant current; Calculate the current difference between the root mean square value and the resonant current reference value; Calculate the adjustment amplitude based on the current difference; The amplitude of the adjustment is limited to obtain the amplitude control value.

4. The control method for the resonant generator according to claim 2, characterized in that, The capacitor voltage is the capacitor voltage of each H-bridge module in the impedance adjustment device; The step of inputting the capacitor voltage into the phase loop to obtain the phase offset includes: Calculate the phase of the resonant current based on the real-time resonant current; The DC capacitor voltage is obtained by averaging the capacitor voltages of each H-bridge module in the impedance adjustment device. Calculate the voltage difference between the DC capacitor voltage and the voltage reference value; Calculate the phase setpoint based on the voltage difference; The sum of the given phase value, the phase of the resonant current, and the preset phase compensation amount is used as the phase offset.

5. The control method for the resonant generator according to claim 1, characterized in that, The impedance adjustment of the impedance adjustment device based on the modulation wave signal control quantity includes: The control quantity of the modulated wave signal is modulated to obtain the driving signal; The driving signal drives the switching elements in the cascaded H-bridge within the impedance adjustment device to adjust the impedance of the impedance adjustment device.

6. The control method for the resonant generator according to claim 1, characterized in that, The method further includes: Soft-start control is applied to the resonant generator; Accordingly, the soft-start control of the resonant generator includes: The soft-start initial stage occurs when the real-time resonant current is less than the first preset threshold; the steady current ramp-up stage occurs when the real-time resonant current is not less than the first preset threshold and is less than the second preset threshold; and the steady-state operation stage occurs when the real-time resonant current is not less than the second preset threshold. In the initial stage of the soft start, the auxiliary power supply of the impedance adjustment device is controlled to output a first preset voltage to provide power, so that the series resonant circuit operates with a first preset resonant current for a first preset time. After the first preset time, the output voltage of the auxiliary power supply of the impedance adjustment device is gradually increased based on a preset voltage interval. When the output voltage of the auxiliary power supply of the impedance adjustment device reaches the rated voltage, the steady current ramp-up stage begins. During the steady current ramp-up phase, based on the preset resonant current interval, the resonant current setpoint of the series resonant circuit is gradually increased until the real-time resonant current reaches the resonant current reference value, after which the steady-state operation phase begins. During the steady-state operation phase, the real-time resonant current and the capacitor voltage are input into the control loop to obtain the modulation wave signal control quantity; and the impedance is adjusted based on the modulation wave signal control quantity.

7. The control method for the resonant generator according to claim 1, characterized in that, The method further includes: The resonant generator is subjected to soft shutdown control; Accordingly, the soft shutdown control of the resonant generator includes: Based on a preset voltage interval, the voltage reference value is reduced, causing the capacitor voltage to decrease; After the capacitor voltage reaches a preset safe voltage threshold, the reference value of the resonant current is reduced based on a preset resonant current interval. After the real-time resonant current drops to 0, the current voltage reference value is reduced based on a preset voltage interval, and the resonant generator is shut down after the capacitor voltage drops to 0.

8. A controller, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method as described in any one of claims 1 to 7.

9. A resonant generator, characterized in that, It includes a power supply forming a series resonant circuit, a resonant device, an impedance adjustment device, and a controller as described in claim 8; the resonant generator is used to connect to the device under test. The impedance adjustment device consists of cascaded H-bridges, which are composed of multiple H-bridge modules. Each H-bridge module includes an H-bridge sub-module consisting of four switching elements and a capacitor connected in parallel with the H-bridge sub-module.

10. The resonant generator according to claim 9, characterized in that, When the resonant generator is connected in series with the device under test (DUT), the resonant generator is used to perform vector detection on the DUT; when the resonant generator is connected in parallel with the DUT, the resonant generator is used to perform withstand voltage testing on the DUT; wherein, when the resonant generator is connected in parallel with the DUT, the DUT is connected in parallel across the two ends of the resonant generator.

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