Energy storage system drive control method and device

Abstract

A kind of energy storage system drive control method, when detecting that energy storage system switches from grid-connected to off-grid operation, then obtain first duration and second duration, first duration is the total duration of the conduction of second switch tube in the preset period before switching off-grid, second duration is the rated charging duration of the bootstrap capacitor;If first duration is greater than second duration, then determine the first target voltage value of inverter start;If first duration is less than or equal to second duration, then stop inverter control, and after determining that load relay is effectively disconnected, enter controlled power supply stage, and charge bootstrap capacitor by controlling second switch tube;When controlled power supply stage meets first condition, control load relay to attract;When controlled power supply stage meets second condition, exit controlled power supply stage and determine the second target voltage value of inverter start;Based on first target voltage value or second target voltage value, selectively conduct first switch tube or second switch tube to drive control energy storage system.

Description

Technical Field

[0001] This invention relates to the field of energy storage system technology, and in particular to a drive control method and device for an energy storage system. Background Technology

[0002] Energy storage systems connect the grid and loads via a half-bridge inverter circuit, such as... Figure 1 As shown, this is a common half-bridge inverter circuit that integrates parallel and off-grid operation. To reduce costs and the number of components, the half-bridge drive design uses a bootstrap circuit to provide drive power to the upper transistor G1.

[0003] However, during standby operation in grid-connected mode, the charge in the bootstrap capacitor gradually leaks because neither the upper nor lower transistors are switching on or off. When the grid is suddenly lost and a switch to off-grid mode is required, the bootstrap capacitor voltage may not be sufficient to meet the upper transistor's conduction requirements, causing the inverter to fail to operate immediately.

[0004] To address this issue, a bootstrap capacitor charging mode needs to be added during off-grid operation. However, this addition introduces the following problems: 1) It prolongs the grid-to-off-grid switching time, potentially causing power outages to sensitive loads; 2) By controlling the charging process of the bootstrap capacitor, a voltage will be output to the user end, but this voltage is not the standard sinusoidal voltage inherited from the grid loss angle, potentially damaging the user end load. Therefore, existing energy storage systems suffer from long switching times and abnormal output voltages during grid-to-off-grid switching. Summary of the Invention

[0005] This invention provides a drive control method for an energy storage system, aiming to solve the problems of long switching time and abnormal output voltage in existing energy storage systems during grid-connected to off-grid switching. By detecting the total conduction time of the lower transistor within a preset time period before grid-connected to off-grid switching, the method accurately identifies whether the residual charge of the bootstrap capacitor meets the conditions for the upper transistor to conduct. If the conditions are met, the system can quickly switch off-grid and enter normal response; if not, the load relay is first disconnected to ensure the safety of sensitive loads, and the lower transistor is driven to replenish the power to the bootstrap capacitor. When the conditions are met again, the load relay is controlled to engage, so that the relay action time overlaps with the replenishment time, thereby shortening the switching time. By inheriting the phase of the inverter during grid loss, the phase continuity of the output voltage is ensured, and a stable and standard sine wave voltage is established before the load is connected, ensuring power supply quality.

[0006] In a first aspect, embodiments of the present invention provide a drive control method for an energy storage system, applied to an energy storage system including a half-bridge inverter circuit. The half-bridge inverter circuit includes a first switch and a second switch, which alternately conduct to supply power to a load. The half-bridge inverter circuit also includes a bootstrap circuit containing a bootstrap capacitor. When the second switch is turned on, the bootstrap capacitor forms a charging circuit through the second switch. When the first switch needs to be turned on, the bootstrap capacitor provides a drive power supply higher than its source potential. The drive control method for the energy storage system includes the following steps:

[0007] When the energy storage system is detected to switch from grid-connected to off-grid operation, a first duration and a second duration are obtained. The first duration is the total conduction duration of the second switch during a preset period before switching to off-grid operation, and the second duration is the rated charging duration of the bootstrap capacitor.

[0008] If the first duration is greater than the second duration, then the first target voltage value for inverter startup is determined;

[0009] If the first duration is less than or equal to the second duration, the inverter control is stopped, and after the load relay is confirmed to be effectively disconnected, the controlled power supply stage is entered, and the bootstrap capacitor is charged by controlling the second switching transistor; when the first condition is met in the controlled power supply stage, the load relay is controlled to engage; when the second condition is met in the controlled power supply stage, the controlled power supply stage is exited and the second target voltage value for inverter startup is determined.

[0010] Based on the first target voltage value or the second target voltage value, the first switch or the second switch is selectively turned on to drive and control the energy storage system.

[0011] Optionally, determining that the load relay is effectively disconnected includes: sending a disconnect command to the load relay in the half-bridge inverter circuit, and determining whether the sending time of the disconnect command is greater than the effective disconnection time of the load relay; if so, determining that the load relay is effectively disconnected.

[0012] Optionally, entering the controlled charging stage, by controlling the second switch to charge the bootstrap capacitor, includes: disabling the drive signal of the first switch; calculating the duty cycle of the second switch based on the DC bus voltage and the inverter side voltage, and periodically driving the second switch to conduct.

[0013] Optionally, the duty cycle of the second switch is:

[0014] ;

[0015] Where i represents the i-th drive, Duty_i is the duty cycle of the second switch, Duty_min is the preset minimum duty cycle, Vinv_i is the inverter-side voltage, and Vbus_i is the DC bus voltage.

[0016] Optionally, the first condition is:

[0017] ;

[0018] Where T2 is the second duration, T1 is the first duration, T3 is the current charging accumulation duration of the controlled charging phase, Duty_i is the duty cycle of the i-th drive cycle, T_sw is the period of the drive signal, n is the n-th drive cycle experienced at the current moment, and T4 is the activation duration of the load relay.

[0019] Optionally, the second condition is: T3+T1>T2; where T3 is the current accumulated charging time, T1 is the first time, and T2 is the rated charging time.

[0020] Optionally, determining the first target voltage value for inverter startup includes: obtaining the angle at the moment of grid connection to off-grid transition as a first angle; and calculating the first target voltage value for inverter startup based on the first angle.

[0021] Optionally, determining the second target voltage value for inverter startup includes: obtaining the accumulated charging time at the moment of exiting the controlled charging phase; calculating the second angle corresponding to inverter startup based on the first angle and the accumulated charging time; and calculating the second target voltage value for inverter startup based on the second angle corresponding to inverter startup.

[0022] Optionally, the step of selectively turning on the first switch or the second switch to drive and control the energy storage system based on the first target voltage value or the second target voltage value includes: determining whether the target voltage value is greater than or equal to 0, wherein the target voltage value is the first target voltage value or the second target voltage value; if the target voltage value is greater than or equal to 0, then selectively turning on the first switch or the second switch to drive and control the energy storage system based on the sum of the target voltage value and a preset first positive threshold; if the target voltage is less than 0, then selectively turning on the first switch or the second switch to drive and control the energy storage system based on the difference between the target voltage value and the preset first positive threshold.

[0023] Optionally, the step of selectively turning on the first switch or the second switch to drive and control the energy storage system based on the sum of the target voltage value and a preset first positive threshold includes: determining whether the real-time acquired inverter-side voltage is greater than the sum of the target voltage value and the preset first positive threshold; if the inverter-side voltage is greater than the sum of the target voltage value and the preset first positive threshold, then determining to turn on the second switch; if the inverter-side voltage is less than or equal to the sum of the target voltage value and the preset first positive threshold, then determining whether the inverter-side voltage is less than a preset second negative threshold; if the inverter-side voltage is less than the preset second negative threshold, then determining to turn on the first switch; if the inverter-side voltage is greater than or equal to the preset second negative threshold, then setting the bootstrap completion flag.

[0024] Optionally, the step of selectively turning on the first switch or the second switch to drive and control the energy storage system based on the difference between the target voltage value and a preset first positive threshold includes: determining whether the real-time acquired inverter-side voltage is less than the difference between the target voltage value and the preset first positive threshold; if the inverter-side voltage is less than the difference between the target voltage value and the preset first positive threshold, then determining to turn on the first switch; if the inverter-side voltage is greater than or equal to the difference between the target voltage value and the preset first positive threshold, then determining whether the inverter-side voltage is greater than a preset second positive threshold; if the inverter-side voltage is greater than the preset second positive threshold, then determining to turn on the second switch; if the inverter-side voltage is less than or equal to the preset second positive threshold, then setting the bootstrap completion flag.

[0025] Secondly, embodiments of the present invention also provide an energy storage system drive control device, applied to an energy storage system including a half-bridge inverter circuit. The half-bridge inverter circuit includes a first switch and a second switch, the first switch and the second switch being alternately turned on to supply power to the load; the half-bridge inverter circuit further includes a bootstrap circuit, the bootstrap circuit including a bootstrap capacitor; when the second switch is turned on, the bootstrap capacitor forms a charging circuit through the second switch; the bootstrap capacitor provides a drive power supply higher than its source potential to the first switch when the first switch needs to be turned on; the energy storage system drive control device includes:

[0026] The acquisition module is used to detect when the energy storage system switches from grid-connected to off-grid operation, and acquire a first duration and a second duration. The first duration is the total conduction duration of the second switch tube within a preset period before switching to off-grid operation, and the second duration is the rated charging duration of the bootstrap capacitor.

[0027] The first processing module is used to determine the first target voltage for inverter startup if the first duration is greater than the second duration.

[0028] The second processing module is used to stop inverter control if the first duration is less than or equal to the second duration, and after determining that the load relay is effectively disconnected, enter the controlled power supply stage, and charge the bootstrap capacitor by controlling the second switching transistor. When the first condition is met in the controlled power supply stage, the load relay is controlled to engage. When the second condition is met in the controlled power supply stage, the controlled power supply stage is exited and the second target voltage value for inverter startup is determined.

[0029] The control module is used to selectively turn on the first switch or the second switch based on the first target voltage value or the second target voltage value to drive and control the energy storage system.

[0030] In this embodiment of the invention, by detecting the conduction time of the lower transistor before switching from grid connection to off-grid, it accurately identifies whether the current residual charge of the bootstrap capacitor meets the conditions for the upper transistor to conduct. If the conditions are met, the off-grid can be quickly switched to enter normal response. If the conditions are not met, it is determined that the bootstrap capacitor needs to be recharged. Before recharging, the load relay is disconnected to prevent abnormal voltage during the charging process from damaging the load. During the recharging process, the load relay is notified to close in advance, so that the relay action time overlaps with the charging time, further shortening the power outage time perceived by the user. By inheriting the phase of the inverter when the grid is lost, the phase continuity of the output voltage is ensured, and a stable and standard sine wave voltage is established before the load is connected, ensuring power supply quality. Attached Figure Description

[0031] Figure 1 This is a common parallel-to-off-grid integrated half-bridge inverter circuit provided in the embodiments of the present invention;

[0032] Figure 2 This is a schematic diagram of a bootstrap circuit provided in an embodiment of the present invention;

[0033] Figure 3 This is a flowchart of a drive control method for an energy storage system provided in an embodiment of the present invention;

[0034] Figure 4 This is a flowchart of another energy storage system drive control method provided in an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the structure of an energy storage system drive control device provided in an embodiment of the present invention.

[0036] In this circuit, G1 is the upper transistor, i.e., the first switching transistor; and G2 is the lower transistor, i.e., the second switching transistor. Detailed Implementation

[0037] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0038] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0039] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] Please see Figure 1 , Figure 1This invention provides a common parallel-to-off-grid integrated half-bridge inverter circuit, which includes a power supply B1, a bus capacitor C3, a capacitor C1, a capacitor C2, a first switch G1, a second switch G2, an inductor L1, a filter capacitor C4, relays JDQ1, JDQ2, JDQ3, and JDQ4, a load LOAD, and a grid GRID. The two ends of power supply B1 are connected to the busbar. The two ends of the busbar capacitor are connected to the busbar. Capacitors C1 and C2 are connected in series at both ends of the busbar to form the first branch. The first switch G1 and the second switch G2 are connected in series at both ends of the busbar to form the second branch. Inductor L1 and filter capacitor C4 form the inverter's filter circuit. One end of inductor L1 is connected to the midpoint of the second branch, and the other end is connected to relay JDQ1 and one end of filter capacitor C4. The other end of filter capacitor C4 is connected to the midpoint of the first branch. The other end of relay JDQ1 is connected to the load LOAD_N and one end of relay JDQ3. The other end of relay JDQ3 is connected to the power grid GRID_N. One end of relay JDQ2 is connected to the midpoint of the first branch. The other end of relay JDQ2 is connected to the load LOAD_L and one end of relay JDQ4. The other end of relay JDQ4 is connected to the power grid GRID_L.

[0041] When relays JDQ1 through JDQ4 are turned on, the energy storage system is in grid-connected mode. When relays JDQ1 and JDQ2 are turned on and JDQ3 and JDQ4 are turned off, the system is in off-grid mode, and the first and second switching transistors alternately turn on to supply power to the load.

[0042] The half-bridge inverter circuit also includes a bootstrap circuit ( Figure 1 (not shown in the image), bootstrap circuit as follows: Figure 2 As shown, the bootstrap circuit includes a driver IC, a bootstrap capacitor Cb, a bootstrap resistor Rb, and a bootstrap diode Db. The driver IC includes Vi, Vcc, Vb, Vo, and Vs terminals. The Vcc terminal is connected to the Vb terminal via the bootstrap resistor Rb and the bootstrap diode Db. The bootstrap capacitor Cb connects between the Vb and Vs terminals. The Vs terminal is connected to the N-terminal of the inverter AC output and the emitter of the upper transistor G1. The Vi terminal is connected to the controller 40 to receive the drive control signal from the controller 40 to the upper transistor (first switching transistor) G1. The Vo terminal is connected to the gate of the upper transistor G1 and outputs a voltage signal to the gate of the upper transistor G1 after receiving the drive control signal at the Vi terminal. The voltage at the Vcc terminal can be 15V~20V. When the lower transistor (second switching transistor) G2 is turned on, it can form... Figure 4The loop shown by the dashed line charges the bootstrap capacitor Cb. When the down transistor G2 is turned off, the voltage of the bootstrap capacitor Cb will not change abruptly, thus maintaining the voltage difference between the Vcc and Vs terminals of the driver IC at approximately 15V. Therefore, although the voltage at the Vs terminal fluctuates with AC changes, after bootstrap charging, the driver IC can meet the driving capability required for the IGBT to turn on at the gate voltage Vge (typically around 15V).

[0043] In this embodiment of the invention, the half-bridge drive design uses a bootstrap capacitor to provide drive power to the upper transistor G1, which can reduce costs and the number of components.

[0044] Please see Figure 3 , Figure 3 This is a flowchart of a drive control method for an energy storage system provided by an embodiment of the present invention. The drive control method for an energy storage system includes the following steps:

[0045] 301. If the energy storage system is detected to switch from grid-connected to off-grid operation, the first duration and the second duration are obtained.

[0046] Grid connection can be understood as the operating state of an energy storage system connected to the power grid, in which electrical energy can flow in both directions. Off-grid connection can be understood as the operating state of an energy storage system disconnected from the power grid, where the energy storage system relies on its own stored energy to supply power.

[0047] The aforementioned first duration refers to the total conduction time of the second switch within a preset time period before switching off the grid. This preset time period can be a pre-set period by the system, such as 50ms or 55ms. The aforementioned total conduction time of the second switch can be understood as the total time length calculated based on the conduction of the second switch in grid-connected mode.

[0048] The second duration mentioned above is the rated charging duration of the bootstrap capacitor. The rated charging duration of the bootstrap capacitor can be understood as the time required for the bootstrap capacitor to charge from 0 to fully charged.

[0049] It should be noted that the system can detect when the energy storage system switches from grid-connected to off-grid operation. The first duration is the total conduction time of the second switch during the preset period before switching off-grid, and the second duration is the rated charging time of the bootstrap capacitor.

[0050] 302. If the first duration is longer than the second duration, then determine the first target voltage value for inverter startup.

[0051] In this embodiment of the invention, the first duration is the total conduction time of the second switch within a preset time period before switching off the grid. The second duration is the rated time of the bootstrap capacitor.

[0052] Furthermore, if the first duration is longer than the second duration, it can be determined that the bootstrap capacitor is fully charged. Therefore, there is no need to recharge the bootstrap capacitor, and the inverter circuit can start directly. It can directly inherit the phase angle at the moment of grid loss and calculate the first target voltage value for inverter start-up based on the angle corresponding to inverter start-up.

[0053] For example, assuming the phase angle at the moment of grid loss is θ_loss, the first target voltage value is calculated as follows: Where V_peak is the peak value of the output voltage when operating off-grid.

[0054] The aforementioned first target voltage value can be understood as the voltage value that the inverter needs to reach during startup in order to enable the load to operate normally.

[0055] 303. If the first duration is less than or equal to the second duration, the inverter control is stopped, and after the load relay is confirmed to be effectively disconnected, the controlled power supply stage is entered, and the bootstrap capacitor is charged by controlling the second switch. When the first condition is met in the controlled power supply stage, the load relay is controlled to close. When the second condition is met in the controlled power supply stage, the controlled power supply stage is exited and the second target voltage value for inverter startup is determined.

[0056] In this embodiment of the invention, if the first duration is less than or equal to the second duration, it can be determined that the bootstrap capacitor is not fully charged, and it is necessary to charge the bootstrap capacitor. Before charging the bootstrap capacitor, the inverter control is stopped and the load relay is disconnected. Then, the controlled charging stage is entered, and the charging process of the bootstrap capacitor is actively isolated from the load. This ensures that during the charging of the bootstrap capacitor, non-standard voltage pulses will never be transmitted to the precision equipment, thus fundamentally preventing load damage.

[0057] Determining that the load relay is effectively disconnected can be achieved by: sending a disconnect command to the load relay in the half-bridge inverter circuit and determining whether the sending time of the disconnect command is greater than the effective disconnection time of the load relay; if so, the load relay is considered to be effectively disconnected. When the effective disconnection time of the load relay is 1ms, if the sending time of the disconnect command is greater than 1ms, the load relay is considered to have been effectively disconnected.

[0058] In the controlled power supply phase, the bootstrap capacitor is charged by controlling the second switch. Specifically, the drive signal of the first switch is disabled; the duty cycle of the second switch is calculated based on the DC bus voltage and the inverter side voltage, and the second switch is periodically driven to conduct to charge the bootstrap capacitor.

[0059] DC bus voltage can be acquired by data acquisition. Figure 1 The voltage across capacitor C3 on the intermediate bus is obtained; the inverter-side voltage can be obtained by acquiring... Figure 1The voltage across the filter capacitor C4 is obtained.

[0060] The duty cycle of the second switch is the ratio of its on-time in one cycle to the total cycle. The duty cycle of the second switch can be calculated based on the real-time acquired DC bus voltage and inverter-side voltage, as follows:

[0061] ;

[0062] Where i represents the i-th drive, Duty_i is the duty cycle of the second switch, Duty_min is the preset minimum duty cycle, Vinv_i is the inverter-side voltage, and Vbus_i is the DC bus voltage.

[0063] Because the mechanical action of the load relay takes time, during the controlled power replenishment phase, the system calculates the remaining charging time in real time and issues a "close load relay" command in advance before charging is completed. The relay closing action time and the bootstrap capacitor charging time are processed in parallel, instead of waiting sequentially, which minimizes the switching time and reduces the power outage time perceived by the user.

[0064] Calculate the current charging accumulation time based on the duty cycle of the second switch; then estimate the remaining charging time based on the current charging accumulation time, the first time, and the second time; finally, if the remaining charging time is less than the pull-in time of the load relay, the first condition is met.

[0065] The first condition is:

[0066] ;

[0067] Where T2 is the second duration, T1 is the first duration, T3 is the current charging accumulation duration of the controlled charging phase, Duty_i is the duty cycle of the i-th drive cycle, T_sw is the period of the drive signal, n is the n-th drive cycle experienced at the current moment, and T4 is the activation duration of the load relay.

[0068] The pull-in time of the aforementioned load relay can be understood as the time interval from when the coil is energized to when the contacts close.

[0069] The system also needs to determine when to exit the controlled charging phase based on the real-time calculated remaining charging time. The controlled charging phase exits when the second condition is met: T3 + T1 > T2. Similarly, T3 is the current accumulated charging time in the controlled charging phase, T1 is the first duration, and T2 is the rated charging time.

[0070] When T3 + T1 > T2, it indicates that the bootstrap capacitor is fully charged, and the controlled power supply phase can be exited. After exiting the controlled power supply phase, the inverter needs to re-enter inverter control, so the second target voltage value for inverter startup needs to be determined. Similarly, it needs to inherit the phase angle at the moment of grid loss. However, due to the confirmation of effective disconnection of the load relay and the existence of the controlled power supply phase, the phase angle has changed. Therefore, it is necessary to calculate the second angle corresponding to inverter startup based on the phase angle at the moment of grid loss, the pull-in time of the load relay (generally the pull-in time equals the disconnection time), and the charging accumulation time at the moment of exiting the controlled power supply phase. The formula for the second angle θ is:

[0071] ;

[0072] Δt = T4 + T5;

[0073] Where θ_loss is the phase angle at the moment of power grid loss, f is the rated frequency, T4 is the activation duration of the load relay, and T5 is the charging accumulation duration at the moment of exiting the controlled power replenishment phase.

[0074] Based on the second angle θ, the second target voltage value Volt_Obj_2 for inverter startup can be calculated:

[0075] ;

[0076] Where V_peak is the peak value of the output voltage when operating off-grid.

[0077] By calculating the starting angle and starting target voltage under different operating conditions, namely the first target voltage value and the second target voltage value, it is ensured that the voltage output by the inverter is continuous in phase. This is crucial for motor loads, as it can effectively prevent inrush current caused by phase change, protect the load, and improve system reliability.

[0078] 304. Based on the first target voltage value or the second target voltage value, selectively turn on the first switch or the second switch to drive and control the energy storage system.

[0079] In this embodiment of the invention, based on the first or second target voltage value for inverter startup, the first or second switching transistor is selected to drive and control the energy storage system. This is a closed-loop control process. Based on the difference between the target voltage and the actual output voltage (the inverter-side voltage acquired in real time), the system intelligently determines whether to drive the first or second switching transistor, allowing the inverter to quickly and smoothly establish a stable and standard sinusoidal voltage under no-load conditions. When the load relays (JDQ1, JDQ2) close at the end of the second stage, the load is connected to a stable, standard, and synchronized sinusoidal AC power supply, identical to that supplied by the power grid.

[0080] It should be noted that when the first switch is driven, the second switch is in a static waveform generation state. Conversely, when the second switch is driven, the first switch is in a static waveform generation state.

[0081] Specifically, it determines whether the target voltage value is greater than or equal to 0; if the target voltage value is greater than or equal to 0, it selectively turns on the first switch or the second switch to drive and control the energy storage system based on the sum of the target voltage value and the preset first positive threshold; if the target voltage is less than 0, it selectively turns on the first switch or the second switch to drive and control the energy storage system based on the difference between the target voltage value and the preset first positive threshold.

[0082] The first positive threshold can be a pre-set positive threshold voltage value, such as 50V.

[0083] Specifically, based on the sum of the target voltage value and a preset first positive threshold, selectively turning on either the first or second switch to drive and control the energy storage system includes: determining whether the real-time acquired inverter-side voltage is greater than the sum of the target voltage value and the preset first positive threshold; if the inverter-side voltage is greater than the sum of the target voltage value and the preset first positive threshold, then determining to turn on the second switch; if the inverter-side voltage is less than or equal to the sum of the target voltage value and the preset first positive threshold, then determining whether the inverter-side voltage is less than a preset second negative threshold; if the inverter-side voltage is less than the preset second negative threshold, then determining to turn on the first switch; if the inverter-side voltage is greater than or equal to the preset second negative threshold, then setting the bootstrap completion flag.

[0084] The aforementioned preset second negative threshold can be a pre-set negative threshold voltage value, such as -40V. The aforementioned set bootstrapping completion flag is used to indicate that the system has successfully completed the bootstrapping process.

[0085] Specifically, based on the difference between the target voltage value and a preset first positive threshold, selectively turning on either a first or second switch to drive and control the energy storage system includes: determining whether the real-time acquired inverter-side voltage is less than the difference between the target voltage value and the preset first positive threshold; if the inverter-side voltage is less than the difference between the target voltage value and the preset first positive threshold, then determining to turn on the first switch; if the inverter-side voltage is greater than or equal to the difference between the target voltage value and the preset first positive threshold, then determining whether the inverter-side voltage is greater than a preset second positive threshold; if the inverter-side voltage is greater than the preset second positive threshold, then determining to turn on the second switch; if the inverter-side voltage is less than or equal to the preset second positive threshold, then setting the bootstrap completion flag.

[0086] The aforementioned preset second positive threshold can be a pre-set positive threshold voltage value, such as 40V. The absolute values ​​of the second positive threshold and the second negative threshold are equal.

[0087] In this embodiment of the invention, when the energy storage system is detected to switch from grid-connected to off-grid operation, a first duration and a second duration are obtained. The first duration is the total conduction time of the second switch within a preset period before switching off-grid, and the second duration is the rated charging duration of the bootstrap capacitor. If the first duration is greater than the second duration, a first target voltage value for inverter startup is determined. If the first duration is less than or equal to the second duration, inverter control is stopped, and after confirming that the load relay is effectively disconnected, a controlled power supply stage is entered, where the second switch is controlled to charge the bootstrap capacitor. When the first condition is met in the controlled power supply stage, the load relay is controlled to engage. When the second condition is met in the controlled power supply stage, the controlled power supply stage is exited, and a second target voltage value for inverter startup is determined. Based on the first or second target voltage value, the first or second switch is selectively turned on to drive the energy storage system. By detecting the conduction time of the lower transistor before grid-connected switching to off-grid, the system accurately identifies whether the remaining charge of the bootstrap capacitor meets the conditions for upper transistor conduction. If the conditions are met, the system can quickly switch off-grid and enter normal response. If not, it determines that the bootstrap capacitor needs to be recharged. Before recharging, the load relay is disconnected to prevent abnormal voltage during charging from damaging the load. During the recharging process, the load relay is notified to close in advance, so that the relay action time overlaps with the charging time, further shortening the perceived power outage time for users. By inheriting the phase of the inverter when the grid is lost, the phase continuity of the output voltage is ensured, and a stable and standard sine wave voltage is established before the load is connected, ensuring power supply quality. This solves the problem of poor stability of the drive circuit in existing energy storage systems when switching from grid-connected to off-grid.

[0088] It is understood that in the specific implementation of this application, data such as duration data, voltage data, and knowledge data are involved. When the embodiments in this application are applied to specific products or technologies, user permission or consent is required. Furthermore, the collection, use, and processing of related data, as well as the training, deployment, and invocation of algorithm models, must comply with the relevant laws, regulations, and standards of the relevant countries and regions.

[0089] Please see Figure 4 , Figure 4 This is a flowchart of a drive control method for an energy storage system provided in an embodiment of the present invention. The drive control method for an energy storage system includes the following steps:

[0090] 400. Determine if the bootstrap completion flag is equal to 0.

[0091] If the bootstrap completion flag is 0, then proceed to step 401; otherwise, proceed to step 422.

[0092] It should be noted that when the energy storage system detects a grid loss and automatically switches to off-grid operation, it will automatically set the bootstrap completion flag to 0.

[0093] 401. Statistically calculate the first and second durations within the preset time before switching to offline network.

[0094] The first duration is the total conduction time of the second switch within a preset period before switching off the grid, and the second duration is the rated charging time of the bootstrap capacitor. The preset period can be a period pre-set by the system, such as 50ms.

[0095] 402. Determine whether the first duration is longer than the second duration.

[0096] If the first duration is greater than the second duration, proceed to step 410; if the first duration is less than or equal to the second duration, proceed to step 403.

[0097] 403. Stop inverter control and send a command to disconnect the load relay.

[0098] The controlled relays include relay JDQ1 and relay JDQ2.

[0099] 404. Determine whether the time it takes for the disconnect command to be sent is greater than the effective disconnect time of the relay.

[0100] If the disconnect command sending time is greater than the relay's effective disconnect time, then proceed to step 405; otherwise, proceed to step 422.

[0101] 405. Calculate the duty cycle of the second switch.

[0102] The duty cycle of the second switch is denoted as Duty.

[0103] ;

[0104] Here, 5% is the preset minimum duty cycle, Vinv represents the voltage sampling value of the filter capacitor C4 in the half-bridge inverter circuit, and Vbus represents the voltage sampling value of the bus capacitor C3 in the half-bridge inverter circuit. It should be noted that when calculating the duty cycle of the second switch, the first switch is in a disabled waveform state.

[0105] 406. Calculate the current cumulative charging time.

[0106] The current charging accumulation time is the total time interval between the start of charging of the bootstrap capacitor by the second switch and the current charging time during the controlled charging phase.

[0107] 407. Determine whether the remaining charging time is less than the load relay's energizing time.

[0108] If the remaining charging time is less than the load relay's engagement time, then proceed to step 408; otherwise, proceed to step 409.

[0109] The remaining charging time can be calculated using the following formula:

[0110] Remaining charging time = Second duration - First duration - Current accumulated charging time

[0111] The drive cycle can be understood as the time required for the energy storage system to complete a drive control cycle.

[0112] 408. Send a relay energizing signal.

[0113] Among them, the relay activation signal controls the activation of relays JDQ1 and JDQ2, and executes step 409.

[0114] 409. Determine whether the sum of the current accumulated charging time and the first time is greater than the second time.

[0115] If the sum of the current accumulated charging time and the first time is greater than the second time, proceed to step 410; otherwise, proceed to step 422.

[0116] 410. Calculate the angle corresponding to inverter startup.

[0117] The angle corresponding to inverter startup is the trigger angle for the switching transistor to turn on and off.

[0118] 411. Calculate the target voltage value for inverter startup.

[0119] 412. Determine whether the target voltage is greater than or equal to 0.

[0120] If the target voltage is greater than or equal to 0, proceed to step 413; otherwise, proceed to step 417.

[0121] 413. Determine whether the inverter side voltage is greater than the sum of the target voltage value and the preset first positive threshold.

[0122] If the inverter-side voltage is greater than the sum of the target voltage value and the preset first positive threshold, then step 416 is executed; otherwise, step 414 is executed.

[0123] 414. Determine whether the inverter side voltage is less than the preset second negative threshold.

[0124] If the inverter-side voltage is less than the preset second negative threshold, proceed to step 416; otherwise, proceed to step 420.

[0125] 415. First switch drive control.

[0126] Specifically, the first switching transistor is turned on to drive and control the energy storage system.

[0127] 416. Second switch drive control.

[0128] Specifically, the second switch is turned on to drive and control the energy storage system.

[0129] 417. Determine whether the inverter side voltage is less than the difference between the target voltage value and the preset first positive threshold.

[0130] If the inverter-side voltage is less than the difference between the target voltage value and the preset first positive threshold, step 421 is executed; otherwise, step 418 is executed.

[0131] 418. Determine whether the inverter-side voltage is greater than the preset second positive threshold.

[0132] If the inverter-side voltage is greater than the preset second positive threshold, proceed to step 419; otherwise, proceed to step 420.

[0133] 419. Second switch drive control.

[0134] Specifically, the second switch is turned on to drive and control the energy storage system.

[0135] 420. Positioning self-bootstrapping completion flag.

[0136] The set bootstrapping completion flag is a flag used to indicate that the system has successfully completed the bootstrapping process.

[0137] 421. First switch transistor drive control.

[0138] Specifically, the first switching transistor is turned on to drive and control the energy storage system.

[0139] 422. End.

[0140] In this embodiment of the invention, by detecting the conduction time of the second switch before grid connection and disconnection, it accurately identifies whether the current residual charge of the bootstrap capacitor meets the condition for the first switch to conduct. When the current residual charge of the bootstrap capacitor meets the condition for the first switch to conduct, it quickly disconnects from the grid and enters normal response. When the current residual charge of the bootstrap capacitor does not meet the condition for the first switch to conduct, it supplements the charging demand of the missing portion of the second switch, ensuring the stability of the drive circuit while supplementing the deficiency in the shortest possible time. During the process of controlling the second switch to charge the bootstrap capacitor, relays JDQ1 and JDQ2 are actively disconnected to avoid the impact of abnormal voltage during the bootstrap charging process on the user load. By estimating the bootstrap charging completion time, relays JDQ1 and JDQ2 are sent to engage in advance, shortening the time for restoring power to the user and effectively avoiding the risk of power failure of special loads. By actively controlling the charging and discharging of the bootstrap capacitor, the voltage difference between the target voltage and the stored charge in the bus capacitor is reduced, which can effectively reduce the output current surge.

[0141] like Figure 5As shown, this embodiment of the invention provides an energy storage system drive control device, applied to an energy storage system including a half-bridge inverter circuit. The half-bridge inverter circuit includes a first switch and a second switch, which alternately conduct to supply power to the load. The half-bridge inverter circuit also includes a bootstrap circuit, which includes a bootstrap capacitor. When the second switch is turned on, the bootstrap capacitor forms a charging circuit through the second switch. When the first switch needs to be turned on, the bootstrap capacitor provides a drive power supply higher than its source potential. The energy storage system drive control device includes:

[0142] The acquisition module 501 is used to detect when the energy storage system switches from grid-connected to off-grid operation, and acquire a first duration and a second duration. The first duration is the total conduction duration of the second switch tube within a preset period before switching to off-grid operation, and the second duration is the rated charging duration of the bootstrap capacitor.

[0143] The first processing module 502 is used to determine the first target voltage value for inverter startup if the first duration is greater than the second duration.

[0144] The second processing module 503 is configured to: stop inverter control if the first duration is less than or equal to the second duration; and after determining that the load relay is effectively disconnected, enter the controlled power supply stage by controlling the second switching transistor to charge the bootstrap capacitor; enter the controlled power supply stage by controlling the second switching transistor to charge the bootstrap capacitor; when the first condition is met in the controlled power supply stage, control the load relay to engage; and when the second condition is met in the controlled power supply stage, exit the controlled power supply stage and determine the second target voltage value for inverter startup.

[0145] The control module 504 is used to selectively turn on the first switch or the second switch based on the first target voltage value or the second target voltage value to drive and control the energy storage system.

[0146] Optionally, the second processing module 503 is further configured to send a disconnect command to the load relay in the half-bridge inverter circuit, and determine whether the sending time of the disconnect command is greater than the effective disconnect time of the load relay; if so, it is determined that the load relay is effectively disconnected.

[0147] Optionally, the second processing module 503 is further configured to disable the drive signal of the first switch; calculate the duty cycle of the second switch based on the DC bus voltage and the inverter side voltage, and periodically drive the second switch to conduct.

[0148] Optionally, the duty cycle of the second switch is:

[0149] ;

[0150] Where i represents the i-th drive, Duty_i is the duty cycle of the second switch, Duty_min is the preset minimum duty cycle, Vinv_i is the inverter-side voltage, and Vbus_i is the DC bus voltage.

[0151] Optionally, the first condition is:

[0152] ;

[0153] Where T2 is the second duration, T1 is the first duration, T3 is the current charging accumulation duration of the controlled charging phase, Duty_i is the duty cycle of the i-th drive cycle, T_sw is the period of the drive signal, n is the n-th drive cycle experienced at the current moment, and T4 is the activation duration of the load relay.

[0154] Optionally, the second condition is: T3 + T1 > T2.

[0155] Where T3 is the current cumulative charging duration during the controlled charging phase, T1 is the first duration, and T2 is the rated charging duration.

[0156] Optionally, the first processing module 502 is further configured to obtain the angle at the moment of grid connection to off-grid transition as a first angle; and calculate the first target voltage value for inverter startup based on the first angle.

[0157] Optionally, the second processing module 503 is further configured to obtain the charging accumulation time at the moment of exiting the controlled charging phase, calculate the second angle corresponding to inverter start-up based on the first angle and the charging accumulation time, and calculate the second target voltage value for inverter start-up based on the second angle corresponding to inverter start-up.

[0158] Optionally, the control module 504 is further configured to determine whether the target voltage value is greater than or equal to 0, wherein the target voltage value is the first target voltage value or the second target voltage value; if the target voltage value is greater than or equal to 0, then based on the sum of the target voltage value and a preset first positive threshold, selectively turn on the first switch or the second switch to drive and control the energy storage system; if the target voltage is less than 0, then based on the difference between the target voltage value and the preset first positive threshold, selectively turn on the first switch or the second switch to drive and control the energy storage system.

[0159] Optionally, the control module 504 is further configured to determine whether the real-time acquired inverter-side voltage is greater than the sum of the target voltage value and a preset first positive threshold; if the inverter-side voltage is greater than the sum of the target voltage value and the preset first positive threshold, then determine that the second switch is turned on; if the inverter-side voltage is less than or equal to the sum of the target voltage value and the preset first positive threshold, then determine whether the inverter-side voltage is less than a preset second negative threshold; if the inverter-side voltage is less than the preset second negative threshold, then determine that the first switch is turned on; if the inverter-side voltage is greater than or equal to the preset second negative threshold, then set the bootstrap completion flag.

[0160] Optionally, the control module 504 is further configured to determine whether the real-time acquired inverter-side voltage is less than the difference between the target voltage value and a preset first positive threshold; if the inverter-side voltage is less than the difference between the target voltage value and the preset first positive threshold, then determine that the first switch is turned on; if the inverter-side voltage is greater than or equal to the difference between the target voltage value and the preset first positive threshold, then determine whether the inverter-side voltage is greater than a preset second positive threshold; if the inverter-side voltage is greater than the preset second positive threshold, then determine that the second switch is turned on; if the inverter-side voltage is less than or equal to the preset second positive threshold, then set the bootstrap completion flag.

[0161] The above is only one specific implementation of this application, and any other improvements made based on the concept of this application shall be considered within the scope of protection of this application.

Claims

1. A drive control method for an energy storage system, characterized in that, An energy storage system incorporating a half-bridge inverter circuit is provided. The half-bridge inverter circuit includes a first switch and a second switch, which are alternately turned on to supply power to the load. The half-bridge inverter circuit also includes a bootstrap circuit containing a bootstrap capacitor. When the second switch is turned on, the bootstrap capacitor forms a charging circuit through the second switch. When the first switch needs to be turned on, the bootstrap capacitor provides a driving power supply higher than its source potential. The energy storage system drive control method includes the following steps: When the energy storage system is detected to switch from grid-connected to off-grid operation, a first duration and a second duration are obtained. The first duration is the total conduction duration of the second switch during a preset period before switching to off-grid operation, and the second duration is the rated charging duration of the bootstrap capacitor. If the first duration is greater than the second duration, then the first target voltage value for inverter startup is determined; If the first duration is less than or equal to the second duration, the inverter control is stopped, and after the load relay is confirmed to be effectively disconnected, the controlled power supply stage is entered, and the bootstrap capacitor is charged by controlling the second switching transistor. When the first condition is met during the controlled power replenishment phase, the load relay is controlled to engage. When the second condition is met during the controlled power supply phase, the controlled power supply phase is exited and the second target voltage value for inverter startup is determined. Based on the first target voltage value or the second target voltage value, the first switch or the second switch is selectively turned on to drive and control the energy storage system.

2. The energy storage system drive control method as described in claim 1, characterized in that, The determination that the load relay is effectively disconnected includes: Send a disconnect command to the load relay in the half-bridge inverter circuit, and determine whether the sending time of the disconnect command is greater than the effective disconnect time of the load relay; If so, then the load relay is confirmed to be effectively disconnected.

3. The energy storage system drive control method as described in claim 1, characterized in that, The controlled charging phase, which involves controlling the second switch to charge the bootstrap capacitor, includes: Disable the drive signal of the first switching transistor; The duty cycle of the second switch is calculated based on the DC bus voltage and the inverter side voltage, and the second switch is periodically driven to turn on.

4. The energy storage system drive control method as described in claim 3, characterized in that, The duty cycle of the second switch is: Where i represents the i-th drive, Duty_i is the duty cycle of the second switch, Duty_min is the preset minimum duty cycle, Vinv_i is the inverter-side voltage, and Vbus_i is the DC bus voltage.

5. The energy storage system drive control method as described in claim 4, characterized in that, The first condition is: Where T2 is the second duration, T1 is the first duration, T3 is the current charging accumulation duration of the controlled charging phase, Duty_i is the duty cycle of the i-th drive cycle, T_sw is the period of the drive signal, n is the n-th drive cycle experienced at the current moment, and T4 is the activation duration of the load relay.

6. The energy storage system drive control method as described in claim 5, characterized in that, The second condition is: T3 + T1 > T2. Where T3 is the current cumulative charging duration during the controlled charging phase, T1 is the first duration, and T2 is the rated charging duration.

7. The energy storage system drive control method as described in claim 1, characterized in that, Determining the first target voltage value for inverter startup includes: The angle at which the grid connection to off-grid transition occurs is taken as the first angle; Based on the first angle, calculate the first target voltage value for inverter startup.

8. The energy storage system drive control method as described in claim 7, characterized in that, Determining the second target voltage value for inverter startup includes: Obtain the accumulated charging time at the moment of exiting the controlled charging phase, and calculate the second angle corresponding to inverter startup based on the first angle and the accumulated charging time; Based on the second angle corresponding to the inverter start-up, calculate the second target voltage value for inverter start-up.

9. The energy storage system drive control method as described in claim 1, characterized in that, The step of selectively turning on the first switch or the second switch based on the first target voltage value or the second target voltage value to drive and control the energy storage system includes: Determine whether the target voltage value is greater than or equal to 0, wherein the target voltage value is the first target voltage value or the second target voltage value; If the target voltage value is greater than or equal to 0, then based on the sum of the target voltage value and a preset first positive threshold, the first switch or the second switch is selectively turned on to drive and control the energy storage system. If the target voltage is less than 0, then based on the difference between the target voltage value and a preset first positive threshold, the first switch or the second switch is selectively turned on to drive and control the energy storage system.

10. The energy storage system drive control method as described in claim 9, characterized in that, The step of selectively turning on the first switch or the second switch to drive and control the energy storage system based on the sum of the target voltage value and a preset first positive threshold includes: Determine whether the real-time acquired inverter-side voltage is greater than the sum of the target voltage value and a preset first positive threshold; If the inverter-side voltage is greater than the sum of the target voltage value and the preset first positive threshold, then the second switch is turned on. If the inverter-side voltage is less than or equal to the sum of the target voltage value and a preset first positive threshold, then determine whether the inverter-side voltage is less than a preset second negative threshold. If the inverter-side voltage is less than the preset second negative threshold, then the first switch is turned on. If the inverter-side voltage is greater than or equal to a preset second negative threshold, then the bootstrap completion flag is set.

11. The energy storage system drive control method as described in claim 9, characterized in that, The step of selectively turning on the first switch or the second switch to drive and control the energy storage system based on the difference between the target voltage value and a preset first positive threshold includes: Determine whether the real-time acquired inverter-side voltage is less than the difference between the target voltage value and a preset first positive threshold. If the inverter-side voltage is less than the difference between the target voltage value and a preset first positive threshold, then the first switch is turned on. If the inverter-side voltage is greater than or equal to the difference between the target voltage value and a preset first positive threshold, then determine whether the inverter-side voltage is greater than a preset second positive threshold. If the inverter-side voltage is greater than a preset second positive threshold, then the second switch is turned on. If the inverter-side voltage is less than or equal to a preset second positive threshold, then the bootstrap completion flag is set.

12. A drive control device for an energy storage system, characterized in that, An energy storage system incorporating a half-bridge inverter circuit is provided. The half-bridge inverter circuit includes a first switch and a second switch, which are alternately turned on to supply power to the load. The half-bridge inverter circuit also includes a bootstrap circuit containing a bootstrap capacitor. When the second switch is turned on, the bootstrap capacitor forms a charging circuit through the second switch. When the first switch needs to be turned on, the bootstrap capacitor provides a driving power supply higher than its source potential. The energy storage system drive control device includes: The acquisition module is used to detect when the energy storage system switches from grid-connected to off-grid operation, and acquire a first duration and a second duration. The first duration is the total conduction duration of the second switch tube within a preset period before switching to off-grid operation, and the second duration is the rated charging duration of the bootstrap capacitor. The first processing module is used to determine the first target voltage value for inverter startup if the first duration is greater than the second duration. The second processing module is used to stop inverter control if the first duration is less than or equal to the second duration, and after determining that the load relay is effectively disconnected, enter the controlled power supply stage, and charge the bootstrap capacitor by controlling the second switching transistor. When the first condition is met in the controlled power supply stage, the load relay is controlled to engage. When the second condition is met in the controlled power supply stage, the controlled power supply stage is exited and the second target voltage value for inverter startup is determined. The control module is used to selectively turn on the first switch or the second switch based on the first target voltage value or the second target voltage value to drive and control the energy storage system.

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