An energy management device for a modular cascaded converter

Abstract

The present application relates to the field of power electronics, and particularly relates to an energy management device of a modular cascaded converter. The device comprises a collection module, a calculation module, an energy storage unit, a control module, an equalization module and an adjustment module. The collection module is used for real-time collection of capacitor voltage, flywheel speed, load current mutation rate and grid voltage sag depth of a sub-module. The calculation module obtains voltage deviation by comparing the capacitor voltage with a preset rated value, and maps the voltage deviation to a flywheel target speed correction amount according to a preset proportion. The scheme maps the voltage deviation to a speed deviation once and synchronously distributes it, and the flywheel absorbs and releases energy on site, and four-stage closed-loop parallel operation works, which can suppress the voltage in a millisecond level, directly solve the problems of slow equalization response, easy over-limit, easy to cause faults and poor operation stability of the sub-module capacitor voltage under the MMC severe disturbance, and synchronously realize harmonic cancellation and grid oscillation damping.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to an energy management device for a modular cascade converter. Background Technology

[0002] Currently, in the fields of high-voltage direct current transmission (HVDC) and flexible alternating current transmission systems (FACTS), modular cascade converters (MMCs) have become core equipment supporting the flexible and high-capacity power transmission of power systems due to their core advantages of flexible modular design and strong scalability. They are widely used in key scenarios such as cross-regional power grid interconnection and new energy grid connection, and their operational stability is directly related to the power supply reliability of the power grid.

[0003] From a topology perspective, an MMC consists of hundreds or even thousands of independent sub-modules (SMs) connected in series via bridge arms. The energy storage capacitors built into each sub-module are key components for energy buffering and voltage support. Among these, the balance of the capacitor voltages in the sub-modules is particularly important, as it directly determines the smoothness of the converter's output level and the accuracy of power transmission. It is also a core prerequisite for preventing overvoltage damage to power devices such as IGBTs and is the foundation for the stable operation of the MMC.

[0004] However, in actual operation, MMCs often face complex disturbance conditions, such as sudden switching of impulsive loads, voltage dips in the grid, and harmonic distortion. Current traditional capacitor voltage balancing strategies have significant limitations, relying heavily on fixed control parameters or lagging regulation logic, resulting in typically long dynamic response times. Faced with the rapid accumulation or loss of capacitor energy under disturbances, this response speed struggles to quickly adapt to changes in operating conditions, making it difficult to suppress abnormal fluctuations in capacitor voltage in a timely manner. Once the capacitor voltage of an individual submodule exceeds the rated safety threshold, it will directly trigger the submodule's overvoltage protection and enter a locked state, further disrupting the power balance of the bridge arm, leading to asymmetrical operation of the bridge arm, and in severe cases, even causing the entire converter to trip, posing a significant threat to the safe and stable operation of the entire transmission system. Summary of the Invention

[0005] This invention provides an energy management device for a modular cascade converter to solve the problems of slow voltage equalization response of submodule capacitors under severe MMC disturbances, easy over-limit, easy failure, and poor operational stability.

[0006] To solve the above-mentioned technical problems, this application provides the following technical solution:

[0007] An energy management device for a modular cascade converter includes:

[0008] The data acquisition module is used to collect data in real time on the capacitor voltage, flywheel speed, load current sag rate, and grid voltage sag depth of the submodule.

[0009] The calculation module obtains the capacitor voltage and compares it with the preset rated value to obtain the voltage deviation. It maps the voltage deviation to the flywheel target speed correction amount according to the preset ratio, adds the preset rated speed to obtain the instantaneous target speed, and then compares the instantaneous target speed with the obtained flywheel speed to obtain the speed deviation.

[0010] The energy storage unit, integrated inside the submodule, is connected in parallel with the capacitor DC bus via a bidirectional motor driver; it obtains the speed deviation and generates a motor drive or power generation command accordingly, which is then sent to the bidirectional motor driver. Upon receiving the command, the bidirectional motor driver drives the flywheel to accelerate or decelerate.

[0011] The control module acquires the speed deviation and, in conjunction with the preset inner loop proportional-integral calculation, generates a motor drive or generator power command, which is then sent to the bidirectional motor driver. When the capacitor voltage reaches the preset pre-control threshold, the inner loop proportional gain is increased by a preset ratio.

[0012] The balancing module acquires the flywheel speed of each submodule and calculates the average value as a benchmark. It compares the flywheel speed of any submodule with the benchmark to obtain the speed deviation. When the speed deviation exceeds a preset threshold, it generates a speed correction command and sends it to the corresponding submodule. The corresponding submodule inputs the command into the calculation module to update the instantaneous target speed.

[0013] The adjustment module acquires the load current mutation rate as the first data and the grid voltage sag depth as the second data. When the first data exceeds a preset first threshold or the second data exceeds a preset second threshold, it sends a preset strong response command to the energy storage unit. After receiving the command, the energy storage unit increases the gain of the power generation command by a preset ratio. When both the first and second data fall below the preset threshold, it sends a preset normal mode command to the energy storage unit. After receiving the command, the energy storage unit restores the gain of the power generation command to a preset default gain.

[0014] The basic principle and beneficial effects of this scheme are as follows: This scheme provides real-time synchronous data of capacitor voltage and flywheel speed through the acquisition module. The calculation module converts the voltage deviation into speed deviation and distributes it to the four modules of energy storage, control, equalization, and regulation. The energy storage unit immediately adjusts the flywheel kinetic energy based on the deviation. The control module superimposes slow-loop correction, the equalization module uses the average speed instead of voltage sorting, and the regulation module temporarily increases the gain when an impact occurs, forming a four-level closed loop that combines local fast response and energy balance. This allows the capacitor voltage to be absorbed or replenished by the inertial pool in the instant of load change or grid disturbance, suppressing drastic voltage fluctuations from the source, blocking the chain reaction of exceeding limits, and solving the problems of slow response and easy exceeding limits in the background technology.

[0015] Meanwhile, the flywheel speed deviation is hardwired within the submodule, and power commands can reach the driver within microseconds. When a step voltage occurs during DC circuit breaker reclosing, the device absorbs most of the step energy within milliseconds, significantly reducing overshoot. The flywheel acceleration current is a controllable high-frequency component, which superimposes a small speed fluctuation opposite to the bridge arm harmonics on the command channel. The flywheel injects anti-phase harmonic current into the bus, which can reduce the bridge arm harmonics to less than one percent, eliminating the need for an external active filter.

[0016] Furthermore, the balancing module completes the average rotational speed comparison with a single subtraction, reducing the algorithm complexity from quadratic to linear. In a scenario with 500 modules per single bridge arm, this saves several milliseconds of computation time per cycle. The freed-up computing power can be used for status monitoring, which can be handled by a low-cost DSP, significantly reducing hardware costs. By superimposing a rotational speed component that is in phase with and in sync with the low-frequency oscillations of the power grid into the power command, the flywheel rapidly absorbs or releases energy, effectively providing mechanical damping for AC power, suppressing inter-regional power oscillations, and improving the stability of the transmission channel.

[0017] In summary, this solution maps voltage deviation to speed deviation and distributes it synchronously. The flywheel absorbs and releases energy locally, and the four-stage closed-loop system operates in parallel. It suppresses drastic voltage rises and falls in milliseconds, directly solving the problems of slow voltage equalization response, easy limit exceedance, easy failure, and poor operational stability of submodule capacitors under severe MMC disturbances. It also simultaneously achieves harmonic cancellation and grid oscillation damping.

[0018] Furthermore, after receiving the speed deviation, if the deviation is positive, the energy storage unit calculates the product of the absolute value and the preset power coefficient to generate a positive drive power command, which is sent to the bidirectional motor driver via the bus. The driver converts the command into a DC drive current reference value, and the current closed loop compares the measured current with the reference value, outputting a modulation signal to make the motor drive the flywheel to accelerate, and the capacitor supplies power to the motor. If the deviation is negative, the absolute value is calculated and the preset power coefficient is multiplied to generate a reverse power generation command. The driver switches to inverter mode, generates a reverse current reference value, and the current closed loop adjusts to make the flywheel decelerate, and the motor feeds back energy to the capacitor. The current closed loop continuously monitors the difference between the measured current and the reference value, dynamically corrects the modulation signal, until the deviation returns to zero.

[0019] This solution distinguishes energy flow direction based on the positive or negative deviation. During forward drive, the capacitor supplies power to increase flywheel speed; during reverse power generation, the flywheel feeds back energy to replenish the capacitor, precisely completing the conversion between electrical and kinetic energy and preventing abnormal capacitor voltage fluctuations. In this solution, the current closed-loop not only stabilizes the motor's operating current but also suppresses transient capacitor surges. For example, in the chemical industry, when this solution is applied to renewable energy grid-connected scenarios, a sudden drop in wind power output can cause a grid sag. The closed-loop can precisely control the energy feedback rate, preventing sudden voltage spikes and drops that could trigger protection. This solution's autonomous closed-loop requires no additional controller commands, reducing computational burden. For instance, during impulsive load switching, it can respond quickly without global coordination commands, improving the submodule's resistance to local disturbances.

[0020] Furthermore, after the control module acquires the speed deviation, the proportional loop amplifies the deviation according to the current inner loop proportional gain, and then the integral loop integrates the accumulated deviation value. The outputs of the proportional loop and the integral loop are superimposed to form a preliminary power command. If the absolute value of the deviation is greater than the integral separation threshold, the integral loop is paused; if it is less than or equal to the threshold, the integral loop is engaged. When the capacitor voltage reaches the pre-control threshold, the inner loop proportional gain is raised from the default value to the preset ratio, while the integral time constant remains unchanged. The preliminary power command is limited to become the final motor drive or generator power command, which is sent to the bidirectional motor driver for execution via the internal bus.

[0021] The integral separation mechanism suspends integral control to prevent overshoot when the deviation is large, and engages integral control to eliminate steady-state error when the deviation is small, avoiding the contradiction between overshoot and steady-state error in traditional proportional-integral control. When the capacitor voltage approaches the pre-control threshold, the inner-loop proportional gain is adaptively increased to enhance the speed deviation regulation and prevent the voltage from approaching the safety threshold further. For example, when the capacitor voltage fluctuates due to impact loads in industrial plants, it can strengthen regulation in advance to stabilize the voltage. Power command limiting can prevent exceeding the load capacity of the driver and motor, protecting hardware safety. Moreover, the above process requires no additional hardware, only algorithm optimization, which ensures regulation accuracy while adapting to different disturbance scenarios. For example, when the grid voltage drops, it can quickly respond to speed deviations without damaging the equipment.

[0022] Furthermore, the equalization module acquires the real-time flywheel speeds of all sub-modules within the bridge arm according to the sampling period. After removing outliers exceeding physical limits, it performs a weighted average of the remaining speeds. The weight is inversely proportional to the absolute value of the capacitor voltage deviation of the corresponding sub-module; the closer the voltage is to the rated value, the greater the weight. The calculation result serves as the benchmark. For each sub-module, the difference between the real-time flywheel speed and the benchmark is calculated to obtain the speed deviation. The preset threshold changes as a percentage of the benchmark value, and the percentage coefficient adaptively increases as the total power fluctuation of the bridge arm increases. When the absolute value of the speed deviation is greater than the dynamic threshold, the product of the deviation value and the preset adjustment coefficient is calculated. The product result is compared with the maximum speed adjustment range of the flywheel, and the smaller of the two absolute values ​​is taken as the correction amount, generating a speed correction command. The correction command is sent to the corresponding sub-module via the internal bus, and the sub-module adds the correction amount to the instantaneous target speed of the calculation module to complete one equalization adjustment.

[0023] Abnormal speed values ​​are eliminated to ensure accurate baseline calculations and prevent abnormal submodules from interfering with overall balance. The weighted average baseline gives greater weight to submodules with voltages close to their rated values, reducing the impact of submodules with large voltage deviations on the baseline. For example, when a grid voltage dip causes small voltage fluctuations in some submodules, the healthy submodule state can be used as the baseline, preventing baseline shifts from causing further submodule imbalances. Dynamic thresholds adaptively adjust with power fluctuations to prevent frequent false adjustment commands during large power fluctuations. Correction parameters are set to small values ​​to protect the flywheel from overload impacts. Precise command issuance adjusts the target speed to achieve balance. The synergy between the weighted average and dynamic thresholds ensures balance accuracy while reducing ineffective adjustments and lowering submodule energy consumption in scenarios with sudden changes in bridge arm power.

[0024] Furthermore, the adjustment module acquires the first data load current mutation rate and the second data grid voltage sag depth and voltage harmonic distortion rate; it compares the first data with preset mild, moderate, and severe thresholds in sequence, and compares the second data with the same three thresholds in sequence; when the first data reaches the moderate or severe threshold, or the second data reaches the moderate or severe threshold, the adjustment module generates a strong response command based on the threshold level reached, and the command carries the gain increase ratio corresponding to the threshold level; the strong response command is sent to the energy storage unit via the internal bus; after receiving it, the energy storage unit synchronously increases the power generation command gain and the drive power command gain according to the increase ratio in the command, and the increase takes effect immediately and is used for subsequent power command calculation.

[0025] Expanding the acquisition of voltage harmonic distortion rate provides a more comprehensive understanding of grid disturbances, avoiding misjudgments caused by relying on only two data points. A three-level threshold classification accurately distinguishes disturbance intensity, and the gain boost ratio is matched to the threshold level to prevent energy oscillations caused by high gain for small disturbances and insufficient response by low gain for large disturbances. The generation and drive power gains are simultaneously increased to ensure coordinated flywheel energy absorption and release, avoiding capacitor voltage imbalance caused by unilateral gain adjustments. Immediate gain activation ensures rapid intervention and adjustment when disturbances occur. The hierarchical matching effect of thresholds and gains is particularly crucial. For example, when high-power motors in industrial parks cause sudden changes in load current and voltage harmonic distortion during start-up and shutdown, the adjustment module can adapt the gain according to the disturbance level, avoiding excessive adjustment and increased energy consumption under minor disturbances while ensuring rapid stabilization of capacitor voltage under severe disturbances.

[0026] Furthermore, the adjustment module initiates a continuous monitoring cycle after both the load current mutation rate and the grid voltage sag depth are below preset thresholds. The cycle length is one-third of the duration of the previous disturbance. If the load current mutation rate and the grid voltage sag depth remain below the preset thresholds during the monitoring cycle, the adjustment module generates a normal mode command and sends it to the energy storage unit. After receiving the command, the energy storage unit gradually lowers the power generation command gain according to the preset gradient curve, and simultaneously lowers the drive power command gain using the same curve. The slope of the gradient curve is negatively correlated with the recovery speed; the faster the recovery speed, the smaller the slope setting. During the recovery period, the capacitor voltage fluctuation is continuously collected. If the fluctuation exceeds the preset stability threshold, the gain reduction is immediately paused and the current gain is maintained. Once the fluctuation is below the stability threshold, the gain is lowered along the gradient curve until it returns to the preset default gain.

[0027] The continuous monitoring cycle is correlated with the duration of the preceding disturbance to avoid frequent mode switching during repeated disturbances, while shortening the duration of ineffective monitoring to accelerate recovery. Gradual curve adjustment of gain prevents sudden gain drops from causing capacitor voltage surges, and the slope adapts to the recovery speed to ensure smooth adjustment under different recovery scenarios. Fluctuation monitoring can promptly pause gain reduction to avoid abnormal voltage fluctuations during recovery. The generation and drive power gains are reduced synchronously to ensure energy conversion balance. The cycle length is correlated with the duration of the disturbance. For example, after the grid disturbance caused by gusts at renewable energy power plants ends, if the preceding disturbance lasts for a long time, the monitoring cycle is extended accordingly to avoid mode switching errors caused by brief recurrence of gusts; if the disturbance lasts for a short time, the cycle is shortened to quickly restore normal adjustment, balancing stability and response efficiency.

[0028] Furthermore, the rotational center axis of the flywheel body within the energy storage unit serves as the rotor shaft. An axially sliding mass ring is mounted on the shaft. The inner side of the mass ring is connected to the rotor shaft via a preload spring, and conductive contacts are embedded on its outer edge. The centrifugal force is obtained by multiplying the flywheel speed (squared) by the mass ring's mass and radius. This centrifugal force is compared with the preset pressure of the preload spring, which is set according to the centrifugal force corresponding to the flywheel speed at the capacitor voltage safety threshold. When the centrifugal force exceeds the preset pressure of the preload spring, the mass ring moves axially, the distance of which is determined by the ratio of the centrifugal force to the spring stiffness. The conductive contacts on the outer edge of the mass ring contact the conductive rails of the outer casing. The width of the conductive rails is greater than the width of the conductive contacts to compensate for axial movement. Upon contact due to movement deviation, a mechanical bypass path is formed. The bypass current flows from the conductive rail through the conductive contact to the grounding terminal, simultaneously generating a voltage jump signal. This voltage jump signal is transmitted to the central controller via a shielded wire. The central controller is located within the valve control main control chassis. The central controller records the jump moment and the corresponding submodule number, generates fault location data, and stores it. Multiple sets of arc-shaped gold-plated contacts are evenly distributed along the circumference of the mass ring and connected in parallel with the conductive rail to reduce the average contact resistance. Once the bypass path is activated, it remains open until the centrifugal force is lower than the preset pressure of the preload spring. The preload spring then pushes the mass ring to reset, the conductive contact separates from the conductive rail, the contact signal disappears, and the fault recording ends.

[0029] The mass ring works in conjunction with a preloaded spring. In case of a fault, centrifugal force pushes the ring to form a bypass; after a fault, the spring resets and disconnects the circuit, enabling fault response and recovery without manual intervention. The conductive rail is wider than the contact piece to compensate for movement deviation, and multiple sets of gold-plated contacts reduce contact resistance. This dual design ensures reliable conduction of the bypass path. The voltage jump signal generated upon contact triggers the central controller to record fault information, achieving precise fault location. For example, in a chemical plant's flexible DC converter submodule, component aging causes an abnormally high capacitor voltage. When the flywheel speed exceeds a threshold, the mass ring moves to form a bypass, and the jump signal allows the controller to quickly locate the faulty submodule. This avoids the tedious process of manually inspecting each submodule individually, shortening troubleshooting time and reducing converter downtime losses.

[0030] A metal film resistor is fixedly installed on a rigid printed circuit board between the conductive rail and the grounding terminal of the outer casing. The metal film resistor is welded and connected in series with the conductive rail to form a static ring grounding circuit. The resistance value of the metal film resistor changes with temperature at a rate lower than a preset threshold. The voltage across the current-limiting resistor is sampled in real time, and the sampled value is transmitted to the central controller via a shielded twisted pair cable. The central controller compares the sampled voltage with a preset voltage limit. When the sampled voltage exceeds the preset limit, a secondary overcurrent warning signal is generated and stored. The current-limiting resistor is connected in series with the bypass path. The bypass current flows through the current-limiting resistor and generates a voltage drop. The voltage drop is captured by the sampling module and converted into a digital quantity. The digital quantity is periodically sent to the central controller via the internal bus. The central controller completes the comparison and warning recording in the next control cycle.

[0031] A PTFE guide ring is fitted around the outer circumference of the mass ring, and slides in axial guide groove with the rotor shaft. An arc-shaped storage groove is opened at the bottom of the guide groove, which is filled with high-temperature grease. The grease is gradually released to the guide surface during sliding. The elastic sealing lip on the inner side of the guide ring is interference-fitted with the rotor shaft to form a sealing interface, preventing grease from overflowing and blocking dust from entering the guide gap. The amount of grease released is determined by the sliding displacement and the sealing lip clamping force. The amount of grease released increases when the displacement increases, while the sealing lip clamping force remains constant to ensure a continuous lubricating film. The wear of the sealing lip is calculated by the wear coefficient of the guide ring material and the cumulative number of sliding cycles. The wear data is read periodically through the maintenance interface to predict the replacement cycle.

[0032] The metal film resistor serves as both a current limiter and a voltage sampling carrier, limiting bypass inrush current and triggering overcurrent warnings through voltage monitoring, thus achieving dual functions of hardware protection and signal feedback. The PTFE guide ring, in conjunction with a grease reservoir, automatically releases grease during sliding, with the release amount adapting to displacement. This reduces friction and wear while preventing insufficient or excessive lubrication. The sealing lip prevents grease overflow and dust intrusion, and its wear data can predict replacement cycles, avoiding sudden failures. The adaptive grease release based on displacement is crucial; for example, when the mass ring of a metro traction converter submodule frequently slides due to train starts and stops, this design ensures sufficient lubrication on the guide surface, avoiding localized dry friction that occurs with traditional fixed lubrication methods under high-frequency sliding. Furthermore, wear data allows maintenance personnel to plan replacements in advance, reducing metro downtime for maintenance.

[0033] Furthermore, it also includes built-in hardware fast response components and software fine optimization modules; the hardware fast response components include a centrifugal force electrical contact linkage mechanism and a fast-blowout unit. The linkage mechanism obtains centrifugal force by multiplying the square of the flywheel speed by the mass and radius of the mass ring. When the centrifugal force exceeds the pressure of the preload spring, the mass ring moves axially, and the conductive contact plate contacts the stationary conductive rail. The contact voltage jump signal is sent to the central controller via a high-speed isolation line. The fast-blowout unit blows when the instantaneous value of the bridge arm current exceeds the preset blowout threshold. The blowout status signal is sent to the central controller via optical fiber. After receiving any high-priority interrupt signal, the central controller immediately suspends the global energy scheduling algorithm and only retains the fault status data acquisition process.

[0034] The software fine-tuning module starts after the hardware completes fault isolation. It calls the prediction model trained with historical disturbance data, inputs the current capacitor voltage and flywheel speed of each submodule, and outputs the predicted energy demand for future periods. After rolling optimization calculation, it generates an energy scheduling plan. The energy scheduling plan is converted into the target speed correction amount of each submodule. The correction amount is distributed to the calculation module of each submodule via the internal bus. The calculation submodule updates the instantaneous target speed. The updated instantaneous target speed participates in the next round of speed deviation calculation, forming a predictive scheduling closed loop.

[0035] In the hardware rapid response component, the linkage mechanism and fuse unit handle different faults and send signals respectively, which not only quickly isolates the fault to prevent its spread, but also triggers the central controller to pause the scheduling algorithm to retain data, buying time for the software to process. The software fine optimization module starts after hardware isolation, using predictive models and rolling optimization to generate a scheduling plan, which is converted into the target speed correction of the sub-modules to form a closed loop, freeing the software from real-time emergency response to focus on global optimization. In this way, hardware signals drive software process switching and coordination. For example, when a sub-module fault is caused by gusts in an offshore wind power converter station, the hardware quickly isolates the fault, while the software predicts subsequent energy demand based on historical data and adjusts the target speed of other sub-modules in advance. This avoids the lag of traditional methods that rely solely on real-time data adjustment, ensuring both fault handling speed and improving energy utilization efficiency.

[0036] Furthermore, the high-speed isolation line has a built-in filter unit that uses the voltage step change signal generated when the conductive contact plate comes into instantaneous contact with the conductive rail as the contact jump signal. The contact jump signal is output by the edge trigger comparator and the amplitude continuity comparator. The two signals are ANDed to form a verification jump signal, which is sent to the central controller via shielded twisted pair cable. The fuse status signal is converted into Manchester encoding and transmitted through a fiber optic transceiver. The controller decodes the signal with the same clock source to generate a verification fuse signal. After receiving the verification jump signal and the verification fuse signal, the central controller marks the action status of the centrifugal force electric contact linkage mechanism and the fast fuse unit, respectively, and synchronously updates the fault status data acquisition process to ensure accurate correlation of fault information.

[0037] The high-speed isolation line's filtering unit, in conjunction with dual comparators, extracts the effective transition signals generated by the contact of the conductive contacts, while filtering out false signals caused by electromagnetic interference through edge triggering and amplitude continuity verification, preventing the central controller from misjudging faults. Manchester encoding combined with co-current clock decoding ensures stable long-distance transmission of fuse-broken status signals and prevents decoding errors caused by timing deviations. After receiving the signal, the central controller marks the component status and updates the acquisition process, accurately locating faulty hardware and ensuring real-time correlation between fault data and component actions, avoiding information misalignment. The dual comparators also provide interference resistance; for example, in steel plant converter stations, strong electromagnetic interference from surrounding large rolling mills can easily lead to false contact signals in traditional signal transmission. This design eliminates interference through verification, ensuring that a response is triggered only when a genuine fault occurs. Co-current clock decoding, in long-distance bridge arm transmission scenarios in chemical plants, avoids decoding errors of fuse-broken signals caused by clock asynchrony, ensuring accurate fault identification and providing reliable data support for subsequent fault analysis. Attached Figure Description

[0038] Figure 1This is a schematic diagram of the functional module of the energy management device of a modular cascade converter in Embodiment 1 of this scheme.

[0039] Figure 2 This is a flowchart illustrating the dynamic correction of the modulation signal by the energy storage module in Embodiment 1 of this scheme. Detailed Implementation

[0040] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0041] Example 1

[0042] like Figure 1 As shown: An energy management device for a modular cascade converter, comprising:

[0043] The data acquisition module is used to collect data in real time on the capacitor voltage, flywheel speed, load current sag rate, and grid voltage sag depth of the submodule.

[0044] The calculation module acquires the capacitor voltage and compares it with a preset rated value (set by the administrator) to obtain the voltage deviation. It then maps the voltage deviation to a flywheel target speed correction amount according to a preset ratio (set by the administrator), adds the preset rated speed (set by the administrator) to obtain the instantaneous target speed, and finally compares the instantaneous target speed with the acquired flywheel speed to obtain the speed deviation.

[0045] The energy storage unit, integrated inside the submodule, is connected in parallel with the capacitor DC bus via a bidirectional motor driver; it obtains the speed deviation and generates a motor drive or power generation command accordingly, which is then sent to the bidirectional motor driver. Upon receiving the command, the bidirectional motor driver drives the flywheel to accelerate or decelerate.

[0046] The control module acquires the speed deviation and, in conjunction with the preset inner loop proportional gain (set by the administrator), performs integral calculations to generate motor drive or generator power commands, which are then sent to the bidirectional motor driver. When the capacitor voltage reaches the preset pre-control threshold (set by the administrator), the inner loop proportional gain is increased by a preset ratio (set by the administrator).

[0047] The balancing module acquires the flywheel speed of each submodule and calculates the average value as a benchmark. It compares the flywheel speed of any submodule with the benchmark to obtain the speed deviation. When the speed deviation exceeds a preset threshold, it generates a speed correction command and sends it to the corresponding submodule. The corresponding submodule inputs the command into the calculation module to update the instantaneous target speed.

[0048] The adjustment module acquires the load current mutation rate as the first data and the grid voltage sag depth as the second data. When the first data exceeds a preset first threshold (set by the administrator) or the second data exceeds a preset second threshold (set by the administrator), it sends a preset strong response command (set by the administrator) to the energy storage unit. After receiving the command, the energy storage unit increases the gain of the power generation command by a preset ratio (set by the administrator). When both the first and second data fall back below the preset thresholds, the module sends a preset normal mode command (set by the administrator) to the energy storage unit. After receiving the command, the energy storage unit restores the gain of the power generation command to the preset default gain (set by the administrator).

[0049] Specifically, such as Figure 2 As shown, after receiving the speed deviation, if the deviation is positive, the energy storage unit calculates the product of the absolute value and the preset power coefficient (set by the administrator) to generate a positive drive power command, which is sent to the bidirectional motor driver via the bus. The driver converts the command into a DC drive current reference value, compares the measured current with the reference value in the current closed loop, and outputs a modulation signal to make the motor drive the flywheel to accelerate, and the capacitor supplies power to the motor.

[0050] If the deviation is negative, the product of the absolute value and the preset power coefficient is calculated to generate a reverse power generation command. The driver switches to inverter mode, generates a reverse current reference value, and the current closed-loop regulation slows down the flywheel, causing the motor to feed energy back to the capacitor.

[0051] The current closed loop continuously monitors the difference between the measured current and the reference value, dynamically corrects the modulation signal, until the deviation returns to zero.

[0052] Assuming the preset power factor is set to 0.8 kW·s / r (the specific value can be adjusted according to the rated power of the flywheel, e.g., 0.8 for a 10kW flywheel and 1.5 for a 20kW flywheel); a DC driver is selected for the bidirectional motor driver, assuming its current closed-loop sampling frequency is set to 10kHz, and the measured current is collected by the Hall current sensor built into the driver; the upper limit of the DC drive current reference value is set to 1.2 times the rated current of the motor (the specific value is set by the administrator according to the actual usage environment, e.g., if the rated current of the motor is 20A, the upper limit of the reference value is 24A) to avoid motor overload; when the speed deviation returns to zero, the driver automatically enters idle mode to maintain the flywheel speed fluctuation within ±0.5% of the rated speed (the specific value is set by the administrator according to the actual usage environment, e.g., if the rated speed is 2000r / min, the fluctuation is controlled within 1990-2010r / min). The administrator can modify the preset power factor and the upper limit of the current reference value in real time through the "Energy Storage Parameter Configuration" interface on the device's local touch screen.

[0053] Specifically, after the control module obtains the speed deviation, the proportional loop first amplifies the deviation according to the current inner loop proportional gain, and then the integral loop integrates the accumulated deviation value; the output of the proportional loop and the output of the integral loop are superimposed to form the initial power command; if the absolute value of the deviation is greater than the integral separation threshold, the integral loop is paused; if it is less than or equal to the threshold, the integral loop is engaged.

[0054] When the capacitor voltage reaches the pre-controlled threshold, the inner loop proportional gain increases from the default value to the preset ratio, while the integral time constant remains unchanged.

[0055] The initial power command is limited to become the final motor drive or generator power command, which is sent to the bidirectional motor driver for execution via the internal bus.

[0056] Assuming the inner loop proportional gain is set to a default value of 2.5, the pre-control threshold is set to 1.08 times the rated voltage of the submodule capacitor (e.g., if the rated voltage of the capacitor is 1000V, the pre-control threshold is 1080V), and the boost ratio is set to 1.4 times (the default is 2.5, but the boost is 3.5); the integral separation threshold is set to 5% of the rated speed of the flywheel (e.g., if the rated speed is 2000r / min, the threshold is 100r / min); and the initial power command limit is set to ±15kW (the rated power of the matched bidirectional motor is 15kW) to avoid the power command exceeding the hardware's capacity. The proportional-integral parameters of the control module can be remotely modified via the Modbus protocol. Maintenance personnel can enter the parameter values ​​and then enter the "issue command" on the "Control Algorithm Configuration" page of the backend monitoring system for the changes to take effect. During the modification process, the device automatically maintains the current power command to avoid adjustment fluctuations caused by parameter switching.

[0057] Specifically, the equalization module obtains the real-time flywheel speed of all sub-modules in the bridge arm according to the sampling period. After removing outliers that exceed the physical limits, the remaining speeds are weighted and averaged. The weight is inversely proportional to the absolute value of the capacitor voltage deviation of the corresponding sub-module. The closer the voltage is to the rated value, the greater the weight. The calculation result is used as the benchmark.

[0058] For each submodule, the difference between the real-time flywheel speed and the reference speed is calculated to obtain the speed deviation; the preset threshold changes as a percentage of the reference value, and the percentage coefficient is adaptively increased as the total power fluctuation of the bridge arm increases;

[0059] When the absolute value of the speed deviation is greater than the dynamic threshold, the product of the deviation value and the preset adjustment coefficient is calculated. The product result is compared with the maximum speed adjustment range of the flywheel, and the smaller of the two absolute values ​​is taken as the correction amount to generate a speed correction command.

[0060] The correction command is sent to the corresponding sub-module via the internal bus. The sub-module adds the correction amount to the instantaneous target speed of the calculation module to complete one equalization adjustment.

[0061] Assuming the sampling period is set to 50ms (e.g., collecting flywheel speed every 20 times / second to balance real-time performance and hardware load); the physical limit abnormal value of flywheel speed is set to be below 0r / min or above 3000r / min (corresponding to the maximum design speed of the flywheel 3000r / min). After removing abnormal values, if the number of remaining effective speeds is less than 80% of the total number of sub-modules (e.g., only 7 effective out of 10 sub-modules), the balancing module automatically switches to "backup reference" (e.g., taking the average speed within the past 30 seconds); the judgment standard for the total power fluctuation of the bridge arm is "the difference between the current power and the power 1 second ago". If the difference exceeds 10% of the rated power of the bridge arm (e.g., if the rated power of the bridge arm is 50kW and the difference exceeds 5kW), the percentage coefficient of the dynamic threshold is increased from 3% to 5%; the preset adjustment coefficient is set to 0.6, and the maximum speed adjustment range of the flywheel is set to ±200r / min (e.g., if the reference speed is 2000r / min, the corrected speed is not lower than 1800r / min and not higher than 2200r / min).

[0062] Specifically, the adjustment module acquires the first data load current mutation rate and the second data grid voltage sag depth and voltage harmonic distortion rate.

[0063] The first data is compared with the preset mild threshold, moderate threshold, and severe threshold (all set by the administrator) in sequence, and the second data is compared with the same three thresholds in sequence. When the first data reaches the moderate or severe threshold, or the second data reaches the moderate or severe threshold, the adjustment module generates a strong response command based on the threshold level reached, and the command carries the gain increase ratio corresponding to the threshold level.

[0064] The strong response command is sent to the energy storage unit via the internal bus. After receiving the command, the energy storage unit will synchronously increase the gain of the power generation command and the gain of the drive power command according to the boost ratio within the command. The increase will take effect immediately and be used for subsequent power command calculations.

[0065] Assuming the three-level threshold settings for load current mutation rate are: mild 5A / s, moderate 10A / s, and severe 15A / s; the three-level threshold settings for grid voltage sag depth are: mild 5% (e.g., sag from rated voltage 380V to 361V), moderate 10%, and severe 15%; and the three-level threshold settings for voltage harmonic distortion rate are: mild 3%, moderate 5%, and severe 8%; the corresponding gain boost ratios are: 1.5 times when triggered by the moderate threshold, and 2 times when triggered by the severe threshold (e.g., default gain 1.0, 1.5 times after moderate, and 2.0 after severe). The regulation module collects load current through a current transformer and grid voltage through a voltage transmitter. After A / D conversion, the data is transmitted to the calculation unit to ensure the accuracy of threshold judgment.

[0066] Specifically, the adjustment module initiates a continuous monitoring cycle after both the load current mutation rate and the grid voltage sag depth are below preset thresholds. The cycle length is one-third of the duration of the previous disturbance. If the load current mutation rate and the grid voltage sag depth remain below the preset thresholds during the monitoring cycle, the adjustment module generates a normal mode command and sends it to the energy storage unit. After receiving the command, the energy storage unit gradually reduces the power generation command gain according to the preset gradient curve (set by the administrator), and simultaneously reduces the drive power command gain using the same curve. The slope of the gradient curve is negatively correlated with the recovery speed; the faster the recovery speed, the smaller the slope setting. During the recovery period, the capacitor voltage fluctuation is continuously collected. If the fluctuation exceeds the preset stability threshold (set by the administrator), the gain reduction is immediately paused and the current gain is maintained. Once the fluctuation is below the stability threshold, the gain is reduced along the gradient curve until it returns to the preset default gain.

[0067] Assuming the duration of the initial disturbance is calculated from the start of the disturbance until the first or second data falls below the threshold, if the disturbance lasts for 300ms, then the continuous monitoring period is set to 100ms.

[0068] The gradient curve uses a linear gradient, with the slope set according to the recovery speed: assuming the capacitor voltage recovers from 1080V (pre-controlled threshold) to 1000V (rated value) at a speed of 0.5V / ms (fast recovery), the slope is set to 0.2kW / s (e.g., 2.5 seconds for gain to decrease from 1.5 to 1.0); if the recovery speed is 0.2V / ms (slow recovery), the slope is set to 0.5kW / s (e.g., 1 second for gain recovery); the stable threshold for capacitor voltage fluctuation is set to ±2% of the rated voltage (e.g., for a 1000V capacitor, gain adjustment is paused if the fluctuation exceeds 20V). During the recovery process, the adjustment module samples the capacitor voltage every 10ms. If three consecutive samples are within the stable threshold, the gain is further adjusted along the gradient curve.

[0069] The acquisition module synchronously acquires multi-channel voltage and current signals; the central controller uses a microprocessor that supports high-frequency computing and multi-protocol communication; the internal bus uses CANopen bus (e.g., transmission rate of 1Mbps, suitable for anti-interference requirements in industrial scenarios); the flywheel body uses a metal flywheel driven by a permanent magnet synchronous motor (e.g., rotational inertia of 1.2kg・m², suitable for 15kW power requirements).

[0070] Administrators can configure parameters via the device's local touchscreen or remote monitoring software, enter the "System Initialization" page, and set the preset thresholds and coefficients for each module in sequence (such as the preset ratio of the calculation module and the sampling period of the equalization module). During operation and maintenance, data such as speed deviation and capacitor voltage fluctuation can be viewed through the "Fault Log" page. If an adjustment abnormality occurs, the default configuration can be restored through the "Parameter Reset" function, and then gradually optimized and adjusted.

[0071] In specific implementation, for a certain 10kV modular cascade converter device (containing 6 sub-modules, with a single module flywheel rated power of 15kW and a capacitor rated voltage of 1000V), as administrator A, the device deployment is completed in four steps: initial configuration, operation monitoring, disturbance response, and operation and maintenance optimization. The specific process is as follows:

[0072] Before powering on the device, the hardware wiring is checked: the acquisition module uses a data acquisition card to connect the capacitor voltage sensor (e.g., range 0-1500V), flywheel speed encoder (output pulse signal), load current transformer and grid voltage transmitter of each sub-module to ensure synchronous acquisition of multi-channel signals; the internal bus adopts CANopen bus to connect the computing module, control module and other modules to the central controller, and the bus transmission rate is set to 1Mbps to adapt to industrial anti-interference requirements.

[0073] After powering on, enter the "System Initialization" page on the local touchscreen and configure the parameters: Set the preset ratio of the calculation module to 0.3 (e.g., a voltage deviation of 100V corresponds to a speed correction of 30r / min), and the rated speed of the flywheel to 2000r / min; the preset power coefficient of the energy storage unit is 1.2kW・s / r adapted to a 15kW flywheel, and the upper limit of the DC drive current reference value is set to 24A (assuming it is 1.2 times the rated current of a motor of 20A); the default value of the control module's inner loop proportional gain is 2.5, the pre-control threshold is set to 1080V (1.08 times the rated voltage of the capacitor), the boost ratio is 1.4 times, and the integral... The separation threshold is 100 r / min (assuming the rated speed is 5%), and the power command limit is ±15kW; the equalization module sampling period is 50ms, the flywheel speed abnormal value range is set to <0 r / min or >3000 r / min, and the dynamic threshold percentage coefficient is 3% by default; the load current mutation rate of the regulation module is set to three thresholds of 5A / s (mild), 10A / s (moderate), and 15A / s (severe), and the grid voltage sag depth is set to three thresholds of 5%, 10%, and 15%, corresponding to gain increase ratios of 1.0 times (mild, no increase), 1.5 times (moderate), and 2.0 times (severe).

[0074] During device operation, data is monitored in real time through the background monitoring system: the acquisition module synchronously uploads the capacitor voltage of each submodule (assuming it is stable at 980-1020V) and flywheel speed (fluctuation within ±10r / min) every 50ms; when a high-power motor in the plant starts at a certain time and the load current suddenly increases to 12A / s (exceeding the moderate threshold of 10A / s), the regulation module immediately sends a strong response command, the energy storage unit increases the power generation or drive command gain to 1.5 times, the bidirectional motor driver quickly switches to drive mode, and the flywheel accelerates to absorb excess energy from the capacitor to avoid a sudden increase in capacitor voltage; after the disturbance lasts for 300ms, the current drops back to the normal range, the regulation module starts a 100ms monitoring cycle, and after confirming that the data is stable, it sends a normal mode command, and the energy storage unit reduces the gain back to the default value at a slope of 0.3kW / s (capacitor recovery speed adapted to 0.4V / ms), during which the capacitor voltage fluctuation is always <20V (stable threshold).

[0075] In routine maintenance, historical data can be viewed through the "Fault Log" page. For example, if the flywheel speed deviation of submodule 1 was found to exceed 200 r / min (exceeding the dynamic threshold), the log shows that the balancing module automatically issued a correction command, reducing its instantaneous target speed by 120 r / min (assuming a deviation of 200 r / min × adjustment coefficient of 0.6, within the ±200 r / min range). Subsequently, the "Parameter Reset" function was used to adjust the balancing module's backup reference switching cycle from 30 seconds to 20 seconds, further improving the speed of abnormal value handling. Currently, the unit is operating stably, with all modules responding promptly and in coordination, meeting the fluctuating power load requirements of the plant area.

[0076] Example 2

[0077] The difference between this embodiment and Embodiment 1 is that the rotation center shaft of the flywheel body in the energy storage unit is used as the rotor shaft, and a mass ring that can slide axially is mounted on the shaft. The inner side of the mass ring is connected to the rotor shaft through a preload spring, and the outer edge is embedded with conductive contact plates.

[0078] The centrifugal force is obtained by multiplying the flywheel speed by the mass and radius of the mass ring after squaring the speed. The centrifugal force is compared with the preset pressure of the preload spring (set by the administrator). The preset pressure of the preload spring is set according to the centrifugal force corresponding to the flywheel speed based on the capacitor voltage safety threshold. When the centrifugal force is greater than the preset pressure of the preload spring, the mass ring moves axially, and the moving distance is determined by the ratio of centrifugal force to spring stiffness.

[0079] The outer edge of the mass ring's conductive contact plate contacts the outer shell's conductive rail. The width of the conductive rail is greater than the width of the conductive contact plate to compensate for axial movement deviation. After contact, a mechanical bypass path is formed. The bypass current flows from the conductive rail through the conductive contact plate to the grounding terminal, simultaneously generating a voltage jump signal. The voltage jump signal is transmitted to the central controller via a shielded wire. The central controller is located inside the valve control main control chassis. The central controller records the jump time and the corresponding submodule number, generates fault location data, and stores it.

[0080] Multiple sets of arc-shaped gold-plated contacts are evenly distributed along the circumference of the mass ring and connected in parallel with the conductive rail to reduce the average contact resistance. After the bypass path is connected, it remains open until the centrifugal force is lower than the preset pressure of the preload spring. The preload spring pushes the mass ring to reset, the conductive contact separates from the conductive rail, the contact signal disappears, and the fault recording ends.

[0081] The rotor shaft is made of high-strength alloy material, and its surface is precision ground to ensure smooth axial movement. The clearance between the inner ring of the mass ring and the shaft is controlled within a range that is snug and free from jamming. The preload spring is made of corrosion-resistant alloy material and is compressed to the designed preload state using special tooling during installation. Both ends of the spring are tightly abutted against the inner groove of the mass ring and the boss on the shaft, respectively, to ensure uniform transmission of spring force.

[0082] The conductive contacts are made of elastic gold-plated material and are uniformly embedded along the circumferential direction of the outer edge of the mass ring. The embedding depth is such that the outer edge of the contact slightly protrudes from the surface of the mass ring. The conductive rail of the outer shell is made of a high conductivity alloy. During installation, laser calibration is used to ensure alignment with the axial movement trajectory of the mass ring. The rail surface is polished to reduce contact resistance.

[0083] After assembly, a centrifugal force simulation test is conducted: the flywheel is driven to rotate by an external drive device, and the speed is gradually increased. It is observed whether the mass ring moves smoothly under the preset working conditions (set by the administrator), whether the conductive contact plate and the conductive rail make reliable contact, and whether the bypass path is open after contact. At the same time, it is checked whether the preload spring can push the mass ring to accurately reset when the speed drops, to ensure that the mechanical action is consistent with the design expectation.

[0084] Specifically, a metal film resistor is fixedly installed on a rigid printed circuit board between the conductive rail and the grounding terminal of the outer shell. The metal film resistor is welded and connected in series with the conductive rail to form a static ring grounding circuit. The resistance value of the metal film resistor changes with temperature at a rate lower than a preset threshold. The voltage across the current limiting resistor is sampled in real time, and the sampled value is transmitted to the central controller via a shielded twisted pair cable. The central controller compares the sampled voltage with the preset voltage limit (set by the administrator). When the sampled voltage exceeds the preset limit, a secondary overcurrent warning signal is generated and stored.

[0085] A current-limiting resistor is connected in series with the bypass path. The bypass current flows through the current-limiting resistor, generating a voltage drop. The voltage drop is captured by the sampling module and converted into a digital quantity. The digital quantity is periodically sent to the central controller through the internal bus. The central controller completes the comparison and early warning recording in the next control cycle.

[0086] The polytetrafluoroethylene guide ring is fitted around the outer circumference of the mass ring, and the guide ring slides in conjunction with the axial guide groove of the rotor shaft. An arc-shaped storage groove is opened at the bottom of the guide groove, and the storage groove is filled with high-temperature grease. The grease is gradually released to the guide surface during the sliding process. The elastic sealing lip on the inner side of the guide ring is interference-fitted with the rotor shaft to form a sealing interface, preventing grease from overflowing and blocking dust from entering the guide gap.

[0087] The amount of grease released is determined by both the sliding displacement and the sealing lip clamping force. When the displacement increases, the amount of grease released increases, while the sealing lip clamping force remains constant to ensure a continuous lubricating film. The amount of sealing lip wear is calculated by the cumulative wear coefficient of the guide ring material and the number of sliding cycles. The wear data is read periodically through the maintenance interface to predict the replacement cycle.

[0088] The metal film resistor is fixed to a rigid printed circuit board by an insulating bracket. The leads at both ends of the resistor are securely soldered to the conductive rail and grounding terminal, and the solder joints are covered with insulating protective adhesive to prevent oxidation. The voltage sensor of the sampling module is installed close to both ends of the resistor. The sensor output line uses double-shielded twisted-pair cable, and the wiring is kept away from high-voltage circuits to reduce electromagnetic interference.

[0089] The inner ring of the PTFE guide ring is interference-fitted with the outer circumference of the mass ring. During assembly, the guide ring is heated to slightly expand it before being fitted into place. After cooling, a tight fit is formed. After the axial guide groove of the rotor shaft is machined, high-temperature grease is evenly filled into the arc-shaped storage groove using a special tool. The filling amount should be two-thirds of the groove volume to avoid excessive grease overflow.

[0090] The inner elastic sealing lip of the guide ring is made of wear-resistant rubber. During assembly, ensure that the lip fits tightly against the rotor shaft surface without excessive compression, thus guaranteeing a good seal without increasing sliding resistance. During maintenance, connect a dedicated testing device through the device's pre-installed maintenance interface to read the cumulative sliding count of the guide ring and simulated wear data of the sealing lip. Combine this with the operating time to determine if replacement is necessary. When replacing, disassemble the entire mass ring and simultaneously update the guide ring and grease.

[0091] In practice, Administrator B first inspected the core components. This included confirming the rotor shaft's hardness and surface finish, the sliding compatibility of the mass ring, and the elasticity of the preload spring; and preparing specialized tooling, a laser calibrator, and other equipment. During assembly, the shaft and mass ring were cleaned, the preload spring was compressed using the tooling, and the mass ring was fitted to ensure smooth sliding; after the conductive contacts were embedded, conductivity was tested, the conductive rails were laser-calibrated, and polished; after the metal film resistor was fixed and welded, insulating adhesive was applied to ensure reliable grounding circuitry. The guide ring was heated and fitted, filled with grease, and a sealing lip was installed to ensure a tight fit without grease overflow.

[0092] During the joint debugging test, the externally driven flywheel accelerates, and the mass ring moves smoothly when it reaches the preset centrifugal force (set by the administrator). After the contact plate contacts the conductive rail, the controller records the jump signal and fault location data in real time. When the safety threshold is exceeded, the voltage sampling of the current limiting resistor triggers a secondary warning. When the mass ring is manually slidable, the resistance is uniform and the grease forms a continuous oil film. After stopping, the spring pushes the ring back to its original position, and the contact plate separation signal disappears.

[0093] Routine maintenance includes weekly readings of guide ring wear data for timely replacement of spare parts; monthly cleaning of contacts and conductive rails; and quarterly inspection of solder joint adhesive. A capacitor voltage exceeding the threshold was encountered, triggering the flywheel to activate the mass loop. The controller accurately recorded this, and after troubleshooting, the system reset normally, demonstrating that the mechanical and electrical coordination met expectations.

[0094] Example 3

[0095] The difference between this embodiment and Embodiments 1 and 2 is that it also includes a built-in hardware fast response component and a software fine optimization module. The hardware fast response component includes a centrifugal force electrical contact linkage mechanism and a fast fuse unit. The linkage mechanism obtains centrifugal force by multiplying the square of the flywheel speed by the mass and radius of the mass ring. When the centrifugal force exceeds the pressure of the preload spring, the mass ring moves axially, and the conductive contact plate contacts the stationary conductive rail. The contact voltage jump signal is sent to the central controller via a high-speed isolation line. The fast fuse unit blows when the instantaneous value of the bridge arm current exceeds the preset fuse threshold (set by the administrator). The fuse status signal is sent to the central controller via optical fiber. After receiving any high-priority interrupt signal, the central controller immediately suspends the global energy scheduling algorithm and only retains the fault status data acquisition process.

[0096] The software fine-tuning module starts after the hardware completes fault isolation. It calls the prediction model trained with historical disturbance data, inputs the current capacitor voltage and flywheel speed of each submodule, and outputs the predicted energy demand for future periods. After rolling optimization calculation, it generates an energy scheduling plan. The energy scheduling plan is converted into the target speed correction amount of each submodule. The correction amount is distributed to the calculation module of each submodule via the internal bus. The calculation submodule updates the instantaneous target speed. The updated instantaneous target speed participates in the next round of speed deviation calculation, forming a predictive scheduling closed loop.

[0097] Before implementation, verify the compatibility of hardware components: check the assembly clearance of the mass ring, preload spring, and rotor shaft of the centrifugal force electrical contact linkage mechanism to ensure smooth sliding; check the quick-blow unit for external damage, normal pin continuity, and compatibility with the wiring terminals of the bridge arm circuit. On the software side, pre-install the fine optimization module in the central controller, confirm compatibility between the module and the controller's operating system, import historical disturbance datasets for prediction model initialization, and simultaneously debug the data interfaces between the module and the calculation units of each sub-module to ensure smooth command transmission.

[0098] During hardware assembly, precisely align the centrifugal force electrical contact linkage mechanism with the flywheel rotor shaft of the energy storage unit. After fixing, manually push the mass ring to test the axial movement accuracy. Connect the quick-break unit to the bridge arm circuit according to the circuit diagram, and tighten the wiring terminals with a special tool to avoid loosening and poor contact. When wiring the central controller, distinguish between the high-speed isolated line and the fiber optic interface to ensure that the high-priority interrupt signal channel is independent and not mixed with other signal lines.

[0099] During the joint debugging phase, if the capacitor voltage of the simulated submodule exceeds the safety threshold, the flywheel speed increases, triggering the linkage mechanism to move. The mass loop moves, causing the conductive contact to contact the conductive rail. Observe whether the central controller immediately pauses the global energy dispatch algorithm, retaining only the fault data acquisition. After the hardware completes fault isolation, check whether the software module automatically starts the prediction model, inputs the current capacitor voltage and flywheel speed data, generates an energy dispatch plan and converts it into a target speed correction amount, sends it to the submodule calculation unit, and confirms whether the instantaneous target speed is updated, thus forming a closed-loop dispatch.

[0100] Specifically, the high-speed isolation line has a built-in filter unit that takes the voltage step change signal generated when the conductive contact plate comes into instantaneous contact with the conductive rail as the contact jump signal. The contact jump signal is output by the edge trigger comparator and the amplitude continuity comparator. The two signals are ANDed to form a verification jump signal, which is sent to the central controller via shielded twisted pair cable.

[0101] The fuse status signal is converted into Manchester encoding and transmitted through a fiber optic transceiver. The controller decodes the signal using a synchronous clock to generate a verification fuse signal. After receiving the verification jump signal and the verification fuse signal, the central controller marks the action status of the centrifugal force electric contact linkage mechanism and the fast fuse unit, and synchronously updates the fault status data acquisition process to ensure accurate correlation of fault information.

[0102] Before implementing the high-speed isolation line, verify the integrity of the cable shielding layer to ensure there is no damage or copper leakage, and that the built-in filter unit has no bulges. Leave an appropriate length when cutting the cable to avoid excessive pulling during wiring. Fix the cable along the inner wall of the device, away from high-voltage circuits (such as motor power lines) to prevent electromagnetic interference. Connect one end of the isolation line to the signal output terminal of the conductive contact, and the other end to the corresponding interface of the central controller. After wiring, use a multimeter to test the signal continuity.

[0103] For the signal transmission section of the fuse-broken status, first install the fiber optic transceiver and fix it in a well-ventilated location near the controller to avoid high temperatures affecting performance. Connect the transceiver and the signal output of the fast-break unit to the two ends of the fiber optic cable, respectively, and secure the connectors with special clips to prevent them from falling off. When debugging the synchronous clock, synchronize and calibrate the controller clock with the fiber optic transceiver clock to ensure that the encoding and decoding timings are consistent.

[0104] During signal testing, simulate the rapid fuse unit's fuse failure: after triggering the fuse failure action, observe whether the optical fiber transmits the encoded signal, whether the central controller accurately decodes and generates the verification fuse failure signal, and mark the fuse unit's action status; then simulate the contact of the conductive contact piece, check whether the verification switching signal transmitted by the high-speed isolation line is received by the controller, whether the fault status data acquisition process is updated synchronously, and confirm whether the fault information corresponding to the two types of signals is accurately associated without misalignment or delay.

[0105] In practice, Administrator C focused on hardware and software compatibility and proceeded with the work in four steps: preliminary verification, assembly and wiring, joint debugging and testing, and signal verification, to ensure that the new components were seamlessly integrated with the original devices.

[0106] During the initial verification phase, the focus was on confirming hardware compatibility: The mass ring, preload spring, and rotor shaft of the centrifugal force electrical contact linkage mechanism were checked one by one. Manual sliding of the mass ring showed no jamming, and the spring exhibited uniform elastic recovery after being pressed. The quick-blow unit showed no external damage, and its pin continuity was verified using a multimeter. The wiring terminals and bridge arm circuit interfaces were confirmed to be compatible. On the software side, a fine-tuning module was pre-installed on the central controller to verify module compatibility with the controller system. Historical disturbance datasets were imported to initialize the prediction model. The interfaces between the module and sub-module calculation units were debugged, and test commands were sent to confirm no delay in command transmission.

[0107] During hardware assembly, precisely align the centrifugal force electrical contact linkage mechanism with the flywheel rotor shaft of the energy storage unit, and after fixing, manually push the mass ring to ensure smooth axial movement without deviation. Connect the fast-blow fuse unit to the bridge arm circuit according to the circuit diagram, and use special tools to tighten the wiring terminals to prevent loosening. When wiring the central controller, clearly distinguish between the high-speed isolation line and the fiber optic interface, and arrange a separate high-priority interrupt signal channel, which should not be mixed with other lines to prevent signal interference.

[0108] During the joint debugging phase, if the capacitor voltage of the simulated submodule exceeds the safety threshold, the drive device is activated to increase the flywheel speed. After the linkage mechanism is triggered, the mass loop moves, causing the conductive contact to contact the conductive rail. The central controller immediately pauses the global energy scheduling algorithm, retaining only fault data acquisition. After the hardware completes fault isolation, the software fine optimization module automatically starts, reads the current capacitor voltage and flywheel speed, and the prediction model outputs the predicted energy demand value. Through rolling optimization, a scheduling plan is generated, converted into a target speed correction amount, and sent to the submodule. The calculation unit is confirmed to have successfully updated the instantaneous target speed, forming a closed-loop scheduling.

[0109] In the signal verification phase, the high-speed isolated cable was handled first: the cable shielding was checked for damage, and after cutting, an appropriate length was left and fixed along the inner wall of the device, away from high-voltage circuits. After wiring, the signal path was tested for continuity. Fiber optic transceivers were installed in a ventilated area of ​​the controller, with the transceivers and fast-break units at both ends of the fiber optic cable secured with clips. After debugging the same clock to ensure consistent encoding and decoding timing, the fuse unit was simulated to activate. The controller accurately decoded and generated a verification fuse break signal and marked its status. Contact was simulated to verify smooth transmission of transition signals, synchronous updates of fault data, and no misalignment between the two types of signals, thus meeting the overall design requirements.

[0110] The above are merely embodiments of the present invention. The invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are able to access all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. An energy management device for a modular cascade converter, characterized in that, include: The data acquisition module is used to collect data in real time on the capacitor voltage, flywheel speed, load current sag rate, and grid voltage sag depth of the submodule. The calculation module obtains the capacitor voltage and compares it with the preset rated value to obtain the voltage deviation. It maps the voltage deviation to the flywheel target speed correction amount according to the preset ratio, adds the preset rated speed to obtain the instantaneous target speed, and then compares the instantaneous target speed with the obtained flywheel speed to obtain the speed deviation. The energy storage unit, integrated inside the submodule, is connected in parallel with the capacitor DC bus via a bidirectional motor driver; it obtains the speed deviation and generates a motor drive or power generation command accordingly, which is then sent to the bidirectional motor driver. Upon receiving the command, the bidirectional motor driver drives the flywheel to accelerate or decelerate. The control module acquires the speed deviation and, in conjunction with the preset inner loop proportional-integral calculation, generates a motor drive or generator power command, which is then sent to the bidirectional motor driver. When the capacitor voltage reaches the preset pre-control threshold, the inner loop proportional gain is increased by a preset ratio. The balancing module obtains the flywheel speed of each sub-module and calculates the average value as a benchmark; The flywheel speed of any submodule is compared with the benchmark to obtain the speed deviation. When the speed deviation exceeds the preset threshold, a speed correction command is generated and sent to the corresponding submodule. The corresponding submodule inputs the command into the calculation module to update the instantaneous target speed. The adjustment module acquires the load current mutation rate as the first data and the grid voltage sag depth as the second data. When the first data exceeds a preset first threshold or the second data exceeds a preset second threshold, it sends a preset strong response command to the energy storage unit. After receiving the command, the energy storage unit increases the gain of the power generation command by a preset ratio. When both the first and second data fall below the preset threshold, it sends a preset normal mode command to the energy storage unit. After receiving the command, the energy storage unit restores the gain of the power generation command to a preset default gain.

2. The energy management device for the modular cascade converter according to claim 1, characterized in that: After receiving the speed deviation, if the deviation is positive, the energy storage unit calculates the product of the absolute value and the preset power coefficient to generate a positive drive power command, which is sent to the bidirectional motor driver via the bus. The driver converts the command into a DC drive current reference value, compares the measured current with the reference value in the current closed loop, and outputs a modulation signal to make the motor drive the flywheel to accelerate, and the capacitor supplies power to the motor. If the deviation is negative, the product of the absolute value and the preset power coefficient is calculated to generate a reverse power generation command. The driver switches to inverter mode, generates a reverse current reference value, and the current closed-loop regulation slows down the flywheel, and the motor feeds back electrical energy to the capacitor. The current closed loop continuously monitors the difference between the measured current and the reference value, dynamically corrects the modulation signal, until the deviation returns to zero.

3. The energy management device for the modular cascade converter according to claim 1, characterized in that: After the control module obtains the speed deviation, the proportional circuit first amplifies the deviation according to the current inner loop proportional gain, and then the integral circuit integrates the cumulative deviation value. The outputs of the proportional and integral circuits are superimposed to form the initial power command; if the absolute value of the deviation is greater than the integral separation threshold, the integral circuit is paused. If the value is less than or equal to the threshold, the integration process is initiated. When the capacitor voltage reaches the pre-control threshold, the inner loop proportional gain increases from the default value to the preset ratio, while the integral time constant remains unchanged. The initial power command is limited to become the final motor drive or generator power command, which is sent to the bidirectional motor driver for execution via the internal bus.

4. The energy management device for the modular cascade converter according to claim 1, characterized in that: The equalization module obtains the real-time flywheel speed of all sub-modules in the bridge arm according to the sampling period. After removing outliers that exceed the physical limits, the remaining speeds are weighted and averaged. The weight is inversely proportional to the absolute value of the capacitor voltage deviation of the corresponding sub-module. The closer the voltage is to the rated value, the greater the weight. The calculation result is used as the benchmark. For each submodule, the difference between the real-time flywheel speed and the reference speed is calculated to obtain the speed deviation; The preset threshold changes as a percentage of the baseline value, and the percentage coefficient adaptively increases as the total power fluctuation of the bridge arm increases. When the absolute value of the speed deviation is greater than the dynamic threshold, the product of the deviation value and the preset adjustment coefficient is calculated. The product result is compared with the maximum speed adjustment range of the flywheel, and the smaller of the two absolute values ​​is taken as the correction amount to generate a speed correction command. The correction command is sent to the corresponding sub-module via the internal bus. The sub-module adds the correction amount to the instantaneous target speed of the calculation module to complete one equalization adjustment.

5. The energy management device for the modular cascade converter according to claim 1, characterized in that: The adjustment module acquires the first data, load current mutation rate, and the second data, grid voltage sag depth and voltage harmonic distortion rate. The first data is compared with the preset mild threshold, moderate threshold, and severe threshold in sequence, and the second data is compared with the same three thresholds in sequence. When the first data reaches the moderate or severe threshold, or the second data reaches the moderate or severe threshold, the adjustment module generates a strong response command based on the threshold level reached, and the command carries the gain increase ratio corresponding to the threshold level. The strong response command is sent to the energy storage unit via the internal bus. After receiving the command, the energy storage unit will synchronously increase the gain of the power generation command and the gain of the drive power command according to the boost ratio within the command. The increase will take effect immediately and be used for subsequent power command calculations.

6. The energy management device for the modular cascade converter according to claim 1, characterized in that: Once the load current mutation rate and grid voltage sag depth are both below preset thresholds, the regulation module initiates a continuous monitoring cycle, with the cycle length being one-third of the duration of the preceding disturbance. If the load current mutation rate and grid voltage sag depth remain below the preset thresholds during the monitoring cycle, the regulation module generates a normal mode command and sends it to the energy storage unit. Upon receiving the command, the energy storage unit gradually reduces the power generation command gain according to a preset gradient curve, while simultaneously reducing the drive power command gain using the same curve. The slope of the gradient curve is negatively correlated with the recovery speed; the faster the recovery speed, the smaller the slope setting. During the recovery period, the capacitor voltage fluctuation is continuously collected. If the fluctuation exceeds a preset stability threshold, the gain reduction is immediately paused and the current gain is maintained. Once the fluctuation is below the stability threshold, the gain is reduced along the gradient curve until it returns to the preset default gain.

7. The energy management device for the modular cascade converter according to claim 6, characterized in that: The rotation center shaft of the flywheel body in the energy storage unit serves as the rotor shaft, and an axially sliding mass ring is mounted on the shaft. The inner side of the mass ring is connected to the rotor shaft through a preloaded spring, and the outer edge is embedded with conductive contact plates. The centrifugal force is obtained by multiplying the flywheel speed by the mass and radius of the mass ring after squaring the speed. The centrifugal force is compared with the preset pressure of the preload spring. The preset pressure of the preload spring is set according to the centrifugal force corresponding to the flywheel speed based on the capacitor voltage safety threshold. When the centrifugal force is greater than the preset pressure of the preload spring, the mass ring moves axially. The moving distance is determined by the ratio of centrifugal force to spring stiffness. The outer edge of the mass ring's conductive contact plate contacts the outer shell's conductive rail. The width of the conductive rail is greater than the width of the conductive contact plate to compensate for axial movement deviation. After contact, a mechanical bypass path is formed. The bypass current flows from the conductive rail through the conductive contact plate to the grounding terminal, simultaneously generating a voltage jump signal. The voltage jump signal is transmitted to the central controller via a shielded wire. The central controller is located inside the valve control main control chassis. The central controller records the jump time and the corresponding submodule number, generates fault location data, and stores it. Multiple sets of arc-shaped gold-plated contacts are evenly distributed along the circumference of the mass ring and connected in parallel with the conductive rail to reduce the average contact resistance. After the bypass path is connected, it remains open until the centrifugal force is lower than the preset pressure of the preload spring. The preload spring pushes the mass ring to reset, the conductive contact separates from the conductive rail, the contact signal disappears, and the fault recording ends.

8. The energy management device for the modular cascade converter according to claim 7, characterized in that: A metal film resistor is fixedly installed on a rigid printed circuit board between the conductive rail and the grounding terminal of the outer shell. The metal film resistor is welded and connected in series with the conductive rail to form a static ring grounding circuit. The resistance value of the metal film resistor changes with temperature at a rate lower than a preset threshold. The voltage across the current limiting resistor is sampled in real time. The sampled value is transmitted to the central controller via a shielded twisted pair cable. The central controller compares the sampled voltage with the preset voltage limit. When the sampled voltage exceeds the preset limit, a secondary overcurrent warning signal is generated and stored. A current-limiting resistor is connected in series with the bypass path. The bypass current flows through the current-limiting resistor and generates a voltage drop. The voltage drop is captured by the sampling module and converted into a digital quantity. The digital quantity is periodically sent to the central controller through the internal bus. The central controller completes the comparison and early warning recording in the next control cycle. The polytetrafluoroethylene guide ring is fitted around the outer circumference of the mass ring, and the guide ring slides in conjunction with the axial guide groove of the rotor shaft. An arc-shaped storage groove is opened at the bottom of the guide groove, and the storage groove is filled with high-temperature grease. The grease is gradually released to the guide surface during the sliding process. The elastic sealing lip on the inner side of the guide ring is interference-fitted with the rotor shaft to form a sealing interface, preventing grease from overflowing and blocking dust from entering the guide gap. The amount of grease released is determined by both the sliding displacement and the sealing lip clamping force. When the displacement increases, the amount of grease released increases, while the sealing lip clamping force remains constant to ensure a continuous lubricating film. The amount of sealing lip wear is calculated by the cumulative wear coefficient of the guide ring material and the number of sliding cycles. The wear data is read periodically through the maintenance interface to predict the replacement cycle.

9. The energy management device for the modular cascade converter according to claim 8, characterized in that: It also includes built-in hardware fast response components and software fine optimization modules; the hardware fast response components include a centrifugal force electrical contact linkage mechanism and a fast fuse unit. The linkage mechanism obtains centrifugal force by multiplying the square of the flywheel speed by the mass and radius of the mass ring. When the centrifugal force exceeds the pressure of the preload spring, the mass ring moves axially, and the conductive contact plate contacts the stationary conductive rail. The contact voltage jump signal is sent to the central controller via a high-speed isolation line. The fast fuse unit blows when the instantaneous value of the bridge arm current exceeds the preset fuse threshold. The fuse status signal is sent to the central controller via optical fiber. After receiving any high-priority interrupt signal, the central controller immediately suspends the global energy scheduling algorithm and only retains the fault status data acquisition process. The software fine-tuning module starts after the hardware completes fault isolation. It calls the prediction model trained with historical disturbance data, inputs the current capacitor voltage and flywheel speed of each submodule, and outputs the predicted energy demand for future periods. After rolling optimization calculation, it generates an energy scheduling plan. The energy scheduling plan is converted into the target speed correction amount of each submodule. The correction amount is distributed to the calculation module of each submodule via the internal bus. The calculation submodule updates the instantaneous target speed. The updated instantaneous target speed participates in the next round of speed deviation calculation, forming a predictive scheduling closed loop.

10. The energy management device for the modular cascade converter according to claim 9, characterized in that: The high-speed isolation line has a built-in filter unit that takes the voltage step change signal generated when the conductive contact piece comes into instantaneous contact with the conductive rail as the contact jump signal. The contact jump signal is output by the edge trigger comparator and the amplitude continuity comparator. The two signals are ANDed to form a verification jump signal, which is sent to the central controller via shielded twisted pair cable. The fuse status signal is converted into Manchester encoding and transmitted through a fiber optic transceiver. The controller decodes the signal using a shared clock to generate a verification fuse signal. After receiving the verification jump signal and the verification fuse signal, the central controller marks the action status of the centrifugal force electric contact linkage mechanism and the fast fuse unit respectively, and updates the fault status data acquisition process synchronously to ensure accurate correlation of fault information.

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