A Coordinated Power Supply System for Energy Storage Batteries and Distributed Power Sources in Microgrids

Abstract

This invention relates to the field of power system and energy management technology, and in particular to a collaborative power supply system for energy storage batteries and distributed power sources in microgrids. The invention integrates a reverse recovery charge dynamic clamping module into the gate drive circuit of an IGBT module. The reverse recovery charge dynamic clamping module includes: a di / dt sensing unit, a pulse generation unit, a negative voltage injection unit, and a gate clamping execution unit. The di / dt sensing unit collects the rate of change of current flowing through the emitter of the IGBT module in real time, and triggers the pulse generation unit when the rate of change of current exceeds a set threshold. The pulse generation unit generates a delayed control pulse to control the negative voltage injection unit to switch the output voltage to a target voltage value and maintain it for a specified time. The gate clamping execution unit locks the gate potential of the IGBT module based on the target voltage value. This invention ensures that the system maintains low electromagnetic interference, high energy efficiency conversion, and long-term operational reliability during millisecond-level seamless switching.

Description

Technical Field

[0001] This invention relates to the field of power system and energy management technology, and in particular to a power supply system for microgrids that combines energy storage batteries with distributed power sources. Background Technology

[0002] As the energy structure rapidly evolves towards cleaner and more distributed power, microgrids, as a key carrier for achieving efficient renewable energy consumption and reliable local power supply, are receiving increasing attention from academia and industry regarding their system architecture and operation control strategies. In typical microgrid topologies, energy storage batteries and distributed power sources such as photovoltaics are often connected in parallel via a DC bus, relying on bidirectional DC-DC converters to achieve flexible energy scheduling and dynamic balancing. While improving power supply resilience, such collaborative power supply systems also place extremely stringent requirements on the switching performance of power electronic interfaces, especially during the millisecond-level seamless switching between energy storage units and intermittent photovoltaic power sources. The transient behavior of power devices directly determines the system's efficiency, lifespan, and electromagnetic compatibility.

[0003] Current mainstream technologies generally employ soft-switching techniques to reduce the conduction and turn-off losses of the main power transistor during high-frequency switching. Specifically, by introducing resonant inductors, auxiliary switches, or zero-voltage / zero-current switching control strategies, the main insulated-gate bipolar transistor (IGBT) completes its state transition near the voltage or current zero-crossing point, thereby significantly suppressing transient switching stress. This approach does effectively alleviate the thermal load on the main switch under specific operating conditions and improves the overall efficiency of the converter to some extent. However, this optimization path has long focused on the driving timing and voltage / current trajectory control of the main switching device itself, systematically neglecting the dynamic characteristics of the body diode integrated in anti-parallel during commutation—a long-marginalized semiconductor physics phenomenon that is gradually becoming a key bottleneck restricting system performance in high di / dt switching scenarios.

[0004] Ultimately, while the body diode integrated within modern IGBT modules only serves a freewheeling function in the circuit topology, its reverse recovery process profoundly affects the electromagnetic transient behavior of the entire converter circuit. When switching between the energy storage battery and photovoltaic power, due to the sudden change in input source impedance and the release of inductor energy, the current flowing through the body diode rapidly reverses, triggering a non-equilibrium recombination process of minority carriers within it, generating significant reverse recovery charge. Measured data shows that in typical microgrid applications, the reverse recovery charge of the body diode in commercial IGBT modules often exceeds 100 nanocoulombs. The resulting current spikes and voltage overshoots, under the influence of parasitic inductance, form high-frequency oscillations with amplitudes exceeding 15% of the DC bus voltage. More alarmingly, existing soft-switching control logic does not incorporate the recovery characteristics of the body diode into its co-optimization, causing this oscillation not only to result in additional switching losses (measurements show a 30% increase in switching losses) but also to accumulate considerable energy waste on an annual scale—the annual switching losses of one actual operating microgrid project have exceeded 800 kWh. Furthermore, repeated voltage stress significantly accelerates the degradation of the gate oxide layer and the fatigue of the bonding wires in IGBT chips, greatly shortening the service life of the devices and thus threatening the long-term reliability of the entire microgrid system.

[0005] In-depth analysis reveals that the root cause of the aforementioned problems lies in the fact that existing technologies treat the body diode as a passive, ideal freewheeling element, neglecting its inherent carrier storage effect and nonlinear recovery dynamics as a bipolar device. Under high-speed switching conditions, the reverse recovery of the body diode is not instantaneous; the resulting displacement current and parasitic parameters couple, forming an electromagnetic interference source that is difficult to completely suppress using traditional passive buffer circuits. Therefore, simply optimizing the soft-switching conditions of the main switch cannot fundamentally eliminate the secondary oscillations and energy dissipation dominated by the body diode. This technical contradiction, against the backdrop of the increasing comprehensive demands for high efficiency, high reliability, and low maintenance costs in microgrids, has evolved from a secondary factor into a core obstacle restricting the leap in system performance. Summary of the Invention

[0006] To overcome the problems in existing technologies where the integrated diodes within the Insulated Gate Bipolar Transistor (IGBT) module generate significant reverse recovery charge under high di / dt switching conditions, leading to high-frequency voltage oscillations, additional switching losses, and accelerated device aging, this invention proposes a collaborative power supply system for microgrids, combining energy storage batteries and distributed power sources. This system ensures low electromagnetic interference, high energy efficiency, and long-term operational reliability during seamless millisecond-level switching.

[0007] The present invention proposes a microgrid-oriented energy storage battery and distributed power supply collaborative power supply system, comprising: an energy storage battery unit, a bidirectional DC-DC converter, a DC bus, a distributed photovoltaic power supply unit, and a central collaborative controller; The energy storage battery unit is connected to the DC bus through the first power interface circuit and the bidirectional DC-DC converter, and the distributed photovoltaic power unit is connected to the DC bus through the second power interface circuit; the central coordination controller is connected to the energy storage battery unit, the bidirectional DC-DC converter and the distributed photovoltaic power unit respectively. The bidirectional DC-DC converter adopts a full-bridge topology, and its main power switching device is an IGBT module with an integrated diode package; the gate drive circuit of the IGBT module integrates a reverse recovery charge dynamic clamping module. The reverse recovery charge dynamic clamping module includes: a di / dt sensing unit, a pulse generation unit, a negative pressure injection unit, and a gate clamping execution unit; The di / dt sensing unit collects the rate of change of current flowing through the emitter of the IGBT module in real time, and triggers the pulse generation unit when the rate of change of current exceeds the set threshold. The pulse generation unit delays the generation of control pulses to control the negative pressure injection unit to switch the output voltage to the target voltage value and maintain it for a specified time; the gate clamping execution unit locks the gate potential of the IGBT module based on the target voltage value.

[0008] Preferably, the di / dt sensing unit includes a current acquisition component and a comparator; the current acquisition component is used to acquire the rate of change of current flowing through the emitter of the IGBT module in real time and input it into the comparator; the comparator compares the rate of change of current with a set threshold and generates an output signal based on the comparison result.

[0009] Preferably, the current acquisition component uses a Rogowski coil or a current transformer; a threshold setting circuit is connected to one input terminal of the comparator to provide the threshold value.

[0010] Preferably, the pulse generation unit is composed of a Schmitt inverter, an XOR gate, and a monostable multivibrator; the Schmitt inverter shapes the input signal of the pulse generation unit; the shaped input signal and the original input signal are input together to the XOR gate, the XOR gate generates a narrow pulse to trigger the monostable multivibrator, so that it outputs a control pulse after a delay time; the delay time is set by the external RC network that triggers the monostable multivibrator with the narrow pulse.

[0011] Preferably, the negative pressure injection unit includes a charge pump circuit, a high-speed MOSFET switch, and an energy storage capacitor; the charge pump circuit is connected to an external auxiliary power supply to power the high-speed MOSFET switch, the high-speed MOSFET switch turns on after receiving a control pulse and sends a target voltage value to the gate clamping execution unit; the energy storage capacitor is used to maintain the source voltage of the high-speed MOSFET switch.

[0012] Preferably, the gate clamping execution unit is composed of an N-channel MOSFET and a Schottky diode connected in parallel; the gate of the MOSFET is connected to the output terminal of the negative voltage injection unit, and the source is grounded; the drain of the MOSFET and the anode of the Schottky diode are both connected to the signal line of the drive circuit, and the cathode of the Schottky diode is connected to the voltage target value as a reference voltage; when the negative voltage injection unit outputs the voltage target value, the MOSFET is turned on, clamping the gate potential of the IGBT module to the voltage target value.

[0013] Preferably, a hard-wired synchronization interface is established between the central coordinating controller and the reverse recovery charge dynamic clamping module, and the timestamp information of the switching event is transmitted using RS485 differential signal transmission; the timestamp includes a 16-bit microsecond counter value and an 8-bit nanosecond offset; the hard-wired synchronization interface has a transmission rate of 10 Mbps and uses Manchester encoding.

[0014] Preferably, the central coordinating controller adopts a dual-core ARM Cortex-M7 architecture microcontroller, and its control algorithm is based on a five-state finite state machine model, including standby, photovoltaic priority, energy storage discharge, hybrid power supply and fault isolation states; before each state switch, a pre-trigger signal is sent to the reverse recovery charge dynamic clamping module.

[0015] Preferably, the PCB layout of the bidirectional DC-DC converter meets the following conditions: the copper foil width of the power loop is not less than 20mm, and the thickness is 70μm; the loop area between the IGBT module and the DC bus capacitor does not exceed 5cm²; the signal lines of the IGBT module adopt a microstrip line structure with a characteristic impedance of 50Ω, and are grounded throughout; all high-frequency nodes are configured with 0.1μF ceramic capacitors and 10μF polymer capacitors in parallel for decoupling, and the mounting position is no more than 5mm from the center of the IGBT module pins.

[0016] Preferably, an electromagnetic compatibility (EMC) filter network is configured between the input terminal of the DC bus unit and the bidirectional DC-DC converter; the EMC filter network consists of a common-mode choke, an X capacitor, and a Y capacitor.

[0017] The advantages of this invention are: (1) This invention introduces a reverse recovery charge dynamic clamping module and embeds a negative voltage gate pulse control mechanism based on real-time di / dt sensing at the driving circuit level. Starting from the physical nature of semiconductors, it actively intervenes in the reverse recovery dynamics of the body diode, realizing hardware-level dynamic clamping of the reverse recovery charge. This technical solution does not rely on external passive buffer circuits, does not increase the complexity of the main power circuit, and does not sacrifice the system switching speed. It can stably suppress the reverse recovery charge of the body diode to below 20 nanocoulombs under typical microgrid operating conditions, and simultaneously achieves multiple technical effects such as reducing switching losses, suppressing voltage oscillations, and extending the life of power devices. It provides a new hardware architecture paradigm for high-reliability and high-efficiency microgrid collaborative power supply systems.

[0018] (2) This invention introduces a hardware-level dynamic control mechanism into the driving circuit of the bidirectional DC-DC converter, which directly acts on the carrier recombination process of the body diode, thereby suppressing the generation and release of reverse recovery charge at the physical level, ensuring that the system maintains low electromagnetic interference, high energy efficiency conversion and long-term operational reliability during the millisecond-level seamless switching process. Attached Figure Description

[0019] Figure 1 This is a module connection diagram of a microgrid-oriented energy storage battery and distributed power supply collaborative power supply system proposed in this invention; Figure 2 Schematic diagram of the reverse charge recovery dynamic clamping module; Figure 3 This is a flowchart of the state transition process. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] like Figure 1 , Figure 2As shown, the energy storage battery and distributed power supply collaborative power supply system (hereinafter referred to as collaborative power supply system) proposed in this embodiment for microgrids includes an energy storage battery unit 101, a bidirectional DC-DC converter 103, a DC bus 104, a distributed photovoltaic power supply unit 106, a central collaborative controller 107, and a reverse recovery charge dynamic clamping module 203. The energy storage battery unit 101 and the distributed photovoltaic power supply unit 106 are connected in parallel to the DC bus 104 through independent power interface circuits (i.e., a first power interface circuit 102 and a second power interface circuit 105), respectively. The bidirectional DC-DC converter 103 is configured between the energy storage battery unit 101 and the DC bus 104 to adjust the direction and amplitude of the charging and discharging power of the energy storage battery 101. The central coordinating controller 107 is connected to the energy storage battery unit 101, the bidirectional DC-DC converter 103 and the distributed photovoltaic power unit 106 respectively. The central coordinating controller 107 monitors the microgrid's operating status in real time and generates switching commands based on load demand, renewable energy output forecasts and energy storage charge status, controlling the bidirectional DC-DC converter 103 to perform millisecond-level seamless switching between energy storage power supply mode and photovoltaic direct power supply mode.

[0022] The bidirectional DC-DC converter 103 adopts a full-bridge topology. Its main power switching device is an IGBT main power switching device with an integrated diode package, referred to as IGBT module 201. Specifically, it is equivalent to an industrial-grade IGBT module with a center frequency of 20kHz, a rated current of 100A, and a rated voltage of 1200V. The typical reverse recovery charge Qrr of its internal body diode is not less than 100 nanocoulombs. The gate drive signal of IGBT module 201 is generated by an isolated gate drive circuit (referred to as drive circuit) 202. The isolated gate drive circuit 202 is based on the Infineon EiceDRIVER™ 1EDC series isolated gate drive IC with hardware expansion, and has independent negative voltage turn-off capability and high-speed response characteristics.

[0023] The driving circuit 202 also integrates a reverse recovery charge dynamic clamping module 203, which consists of a di / dt sensing unit 204, a pulse generation unit 205, a negative pressure injection unit 206, and a gate clamping execution unit 207.

[0024] The di / dt sensing unit 204 acquires the rate of change of current flowing through the emitter of the IGBT module 201 in real time through a Rogowski coil or a high-bandwidth current transformer. Its bandwidth is not less than 50MHz and its rise time is less than 5 nanoseconds. After the output signal is processed by a high-speed comparator and a threshold setting circuit, when the absolute value of di / dt is detected to exceed the preset threshold of 800A / μs, the pulse generation unit 205 is immediately triggered.

[0025] The pulse generation unit 205 adopts a combination structure of fixed delay logic gate array and monostable multivibrator, specifically composed of Schmitt inverter, XOR gate and monostable multivibrator. The Schmitt inverter shapes the input trigger signal and inputs it together with the original signal to the XOR gate to generate a narrow pulse. The narrow pulse triggers the monostable multivibrator, causing it to output a high-level pulse with a width of 100 nanoseconds after a delay time. The delay time is set by an external RC network, specifically R can be set to a 1.5kΩ resistor and C to a 20pF capacitor.

[0026] The input terminal of the pulse generation unit 205 is connected to the output terminal of the di / dt sensing unit 204, and the output terminal is connected to the enable terminal of the negative voltage injection unit 206. The delay time can be specifically set to 30 nanoseconds. When a trigger signal is received, the pulse generation unit 205 generates a control pulse with a width of 100 nanoseconds and an amplitude of logic high level after a precise delay of 30 nanoseconds. The delay time is set according to the measured data of the carrier storage time of the IGBT module 201 to ensure that the negative voltage pulse is accurately applied at the initial moment when the body diode enters the reverse recovery stage.

[0027] The negative voltage injection unit 206 consists of a charge pump circuit, a high-speed MOSFET switch, and an energy storage capacitor. The input of the charge pump circuit serves as the input terminal of the negative voltage injection unit 206, connected to the system auxiliary power supply +15V. Upon receiving a control pulse, the high-speed MOSFET switch turns on within 10 nanoseconds, transmitting a -5V level to the gate clamping execution unit 207 via a low parasitic inductance path. The output of the high-speed MOSFET switch is the output terminal of the negative voltage injection unit 206, connected to the gate clamping execution unit 207 via low parasitic inductance wiring. The energy storage capacitor is a 10μF FX7R ceramic capacitor, positioned no more than 5mm from the source of the MOSFET switch to maintain voltage stability. The charge pump circuit employs a two-stage Dickson structure, operating at a frequency of 1MHz, with an output ripple of less than 50mV, ensuring negative voltage stability.

[0028] Thus, upon receiving a control pulse, the negative pressure injection unit 206 switches the output voltage from the normal shutdown level of -8V to deep negative voltage of -5V within 10 nanoseconds, and maintains it for 100 nanoseconds before returning to -8V.

[0029] The gate clamping execution unit 207 is directly integrated into the isolated gate drive circuit 202 of the IGBT module 201. Its input is connected to the output of the negative voltage injection unit 206, and its output is connected to the gate pin of the IGBT module 201 through a 0.1Ω damping resistor. The gate clamping execution unit 207 includes a parallel structure of a high-speed N-channel MOSFET and a Schottky diode. The gate of the MOSFET is controlled by the negative voltage injection unit 206, the source is grounded, and the drain is connected to the signal line of the isolated gate drive circuit 202 through a 0.1Ω damping resistor. The anode of the Schottky diode is connected to the signal line of the isolated gate drive circuit 202 through a 0.1Ω damping resistor, and the cathode is connected to the -5V reference point. When the negative voltage injection unit 206 outputs -5V, the MOSFET is turned on, forcibly clamping the gate potential of the IGBT module 201 to -5V. At the same time, the Schottky diode provides a low-impedance discharge path, accelerating the extraction of gate charge, that is, accelerating the sweep-out of minority carriers during the reverse recovery process of the body diode in the IGBT module 201.

[0030] During the switching process between the energy storage battery and the distributed photovoltaic power source, after the central coordinating controller 107 issues a mode switching command, the control logic of the bidirectional DC-DC converter 103 first turns off the currently conducting IGBT module 201, causing its body diode to enter the freewheeling state. Due to the sudden change in source impedance on the photovoltaic side or the battery side, the inductor current quickly transfers to the body diode, causing it to conduct in the forward direction. Subsequently, before the next switching cycle begins, the IGBT on the opposite side is triggered to conduct, forcing the body diode current to reverse and entering the reverse recovery stage. At this time, the di / dt sensing unit 204 detects a rapid drop in current and triggers the reverse recovery charge dynamic clamping module to apply a -5V, 100-nanosecond negative gate voltage pulse to the corresponding IGBT during the initial stage of the body diode's reverse recovery.

[0031] This negative gate voltage pulse enhances the electric field strength in the depletion region of the IGBT collector junction, accelerating the sweep-out process of minority carriers in the bulk and effectively suppressing the reverse recovery current spike caused by carrier recombination. Experimental verification shows that, under this mechanism, the reverse recovery charge Qrr of the body diode is stably controlled below 20 nanocoulombs, and the peak reverse recovery current is reduced by 65%. Consequently, the voltage overshoot induced on the parasitic inductance does not exceed 3% of the DC bus voltage, significantly lower than the level of over 15% without this invention.

[0032] A hard-wired synchronization interface is established between the central coordinating controller 107 and the reverse recovery charge dynamic clamping module 203. RS485 differential signal transmission is used to transmit the timestamp information of switching events, ensuring that the timing alignment error between the clamping action and the power switch switching event is less than ±5 nanoseconds. The transmission rate of the hard-wired synchronization interface is set to 10 Mbps, and Manchester encoding is used to eliminate the effects of clock drift. The timestamp information of the event includes a 16-bit microsecond counter value and an 8-bit nanosecond offset, generated by the controller's hardware timer to ensure the accuracy of the timestamp.

[0033] The PCB layout of the bidirectional DC-DC converter 103 strictly adheres to low parasitic inductance design specifications: the copper foil width of the power loop is no less than 20mm, and the thickness is 70μm; the loop area between the IGBT module 201 and the DC bus capacitor is controlled within 5cm²; the signal lines of the IGBT module 201 adopt a microstrip line structure with a characteristic impedance of 50Ω, and are grounded throughout to suppress crosstalk. All high-frequency nodes are equipped with a 0.1μF ceramic capacitor and a 10μF polymer capacitor connected in parallel for decoupling, and the mounting position is no more than 5mm away from the pins of the IGBT module 201.

[0034] All active components of the reverse charge recovery dynamic clamping module 203 are industrial-grade components with a temperature resistance rating of 150℃, packaged in DFN or QFN to reduce thermal resistance. The entire reverse charge recovery dynamic clamping module 203 is mounted on an aluminum heat sink substrate using thermally conductive silicone grease. The substrate is securely connected to the system's main heat sink with screws, with a contact thermal resistance of less than 0.5 K / W. The module operates in an ambient temperature range of -40℃ to +85℃. Within this range, the amplitude deviation of the negative voltage pulse does not exceed ±0.2V, and the pulse width deviation does not exceed ±5 nanoseconds.

[0035] The central coordinating controller 107 employs a dual-core ARM Cortex-M7 architecture microcontroller with a main frequency of 480MHz, and integrates a hardware floating-point unit and DMA controller. Its control algorithm is based on a state machine model, encompassing five operating states: standby, photovoltaic priority, energy storage discharge, hybrid power supply, and fault isolation. State switching conditions are jointly determined by real-time acquired DC bus voltage, battery SOC, photovoltaic output power, and load power, with a switching decision cycle of 100 microseconds. Before each state switch, the central coordinating controller 107 sends a pre-trigger signal to the reverse recovery charge dynamic clamping module 203 200 microseconds in advance, putting it into a standby state to ensure immediate response when actual current commutation occurs.

[0036] The system is also equipped with an electromagnetic compatibility (EMC) filter network located between the input of the DC bus unit 104 and the bidirectional DC-DC converter 103. This network consists of a common-mode choke, an X capacitor, and a Y capacitor, and complies with CISPR 11 Class A radiated emission limits. Because the high-frequency oscillations caused by the reverse recovery of the body diode are suppressed, the common-mode inductor volume of the EMC filter network is reduced by 25%, and the total capacitance of the X / Y capacitors is reduced by 30%. Under typical operating conditions, the reverse recovery charge Qrr of the body diode is stably controlled below 20 nanocoulombs, the peak reverse recovery current is reduced by 65%, and the voltage overshoot induced on the parasitic inductor does not exceed 3% of the DC bus voltage.

[0037] During long-term operation, the reverse recovery charge dynamic clamping module 203 continuously reduces the switching stress of the IGBT module 201, resulting in a 40% reduction in junction temperature fluctuation, a 25% decrease in the peak electric field strength of the gate oxide layer, and a 50% reduction in the mechanical strain rate of the bond wires. Accelerated life test data shows that under ambient temperature of 85°C and full-load cyclic switching conditions, the IGBT module 201 using this invention achieves a mean time between failures (MTBF) of 120,000 hours, which is 2.3 times higher than the control group without this invention.

[0038] In one specific embodiment, the energy storage battery unit 101 uses lithium iron phosphate (LiFeP) batteries. The photovoltaic (PV) power supply unit 106 is composed of several monocrystalline silicon PV modules, with a peak power of 50kW, an open-circuit voltage of 600V, and a maximum continuous discharge current of 200A. The cells are connected in series and parallel, with a nominal voltage of 400V, a rated capacity of 100Ah, and a maximum continuous discharge current of 200A. Its first power interface circuit 102 includes a pre-charge relay, a main contactor, a fuse, and an EMI filter. The pre-charge circuit consists of a current-limiting resistor and a bypass relay to limit the inrush current during initial power-on. The distributed PV power supply unit 106 consists of several groups of monocrystalline silicon PV modules, with a peak power of 50kW, an open-circuit voltage of 600V, and a maximum power point tracking (MPPT) range of 300V to 550V. Its second power interface circuit 105 integrates a reverse-biased diode, a DC isolating switch, and a secondary surge protection module to ensure safe connection in both islanded and grid-connected modes.

[0039] The bidirectional DC-DC converter adopts a full-bridge topology. The main power switching device is the Infineon FF100R12RT4 IGBT module, which integrates four 1200V / 100A IGBT chips and their corresponding body diodes. The switching center frequency is set to 20kHz. The gate drive signal of each IGBT is generated by an independent isolated drive circuit 202. This drive circuit is based on the Infineon EiceDRIVER™1EDC20I12MH and has been hardware extended, providing +15V turn-on drive and -8V turn-off drive capabilities. The rise / fall time of the drive output is less than 50ns. The emitter pin of the IGBT module 201 is directly connected to the power circuit through a low-inductance connector. The collector is connected to the positive terminal of the high-voltage DC bus, and the emitter is connected to the negative terminal of the bus, forming a complete power path.

[0040] The di / dt sensing unit 204 uses a Pearson 411 Rogowski coil with an inner diameter of 15mm, which can be mounted around the emitter pin of the IGBT module. It has a bandwidth of 60MHz, a rise time of 3.5ns, and an output sensitivity of 0.1V / A·μs. The output of this Rogowski coil is connected to the non-inverting input of the high-speed comparator LMH7322, and the inverting input is connected to an adjustable threshold voltage source. The threshold is set to 80mV, corresponding to a di / dt trigger threshold of 800A / μs. When the detected current change rate exceeds this threshold, the comparator outputs a high-level pulse, which is sent as a trigger signal to the pulse generation unit.

[0041] The pulse generation unit 205 is composed of a 74LVC1G14 Schmitt inverter, a 74LVC1G86 XOR gate, and a 74LVC1G123 monostable multivibrator. The Schmitt inverter shapes the input trigger signal and then inputs it along with the original signal to the XOR gate, generating a narrow pulse with a width equal to the inverter's propagation delay. This narrow pulse then triggers the monostable multivibrator, which is configured to output a 100ns high-level pulse with a 30ns delay after receiving the rising edge. The delay time is precisely set via an external RC network: R = 1.5kΩ, C = 20pF. The measured delay time is 30±2ns, which closely matches the carrier storage time (typically 28ns) of the IGBT module FF100R12RT4. This 100ns pulse is sent as an enable signal to the negative pressure injection unit.

[0042] The negative voltage injection unit 206 consists of a two-stage Dickson charge pump, a high-speed MOSFET switch, and an energy storage capacitor. The charge pump input is the system auxiliary power supply +15V, which generates a -12V intermediate voltage through two cascaded diode-capacitor networks driven by a 1MHz clock. This voltage is then regulated by a low-dropout linear regulator (LDO) to output a stable -5V reference. The high-speed MOSFET switch is an Infineon BSC028N06LS3G with an on-resistance Rds(on) of 2.8mΩ, a gate charge Qg of 28nC, and a switching time of less than 10ns. When the enable signal arrives, the MOSFET turns on, delivering the -5V level to the gate clamping actuator through a low parasitic inductance path (length <10mm, width >5mm). The energy storage capacitor is a 10μF FX7R ceramic capacitor, positioned close to the MOSFET source to ensure transient response capability. The measured output ripple of the entire negative voltage injection unit 206 is less than 40mVpp.

[0043] The gate clamping execution unit 207 is directly integrated at the end of the IGBT gate drive circuit 202. Its core consists of an N-channel MOSFET (model BSS138) and a Schottky diode (model BAT54S) connected in parallel. The drain of the BSS138 is connected to the IGBT gate drive signal line, the source is grounded, and the gate receives the output signal from the negative voltage injection unit. The anode of the BAT54S is also connected to the IGBT gate drive signal line, and the cathode is connected to the -5V reference point. In the normal off state, the IGBT gate is clamped at -8V by the drive IC. When the negative voltage injection unit outputs -5V, the BSS138 is turned on, and its on-resistance is approximately 3.5Ω. It is connected in parallel with the internal pull-down path of the drive IC, forcibly raising the IGBT gate potential to -5V (since -5V > -8V, it actually "reduces" the absolute value of the negative voltage). At the same time, the BAT54S provides a low-impedance discharge path from the gate to -5V, with a forward voltage drop of only 0.3V, which significantly accelerates the gate charge extraction process. A 0.1Ω / 1W metal film resistor is connected in series between the execution unit and the IGBT gate to suppress high-frequency oscillations and limit peak current.

[0044] During system operation, the central coordinating controller 107 is implemented based on a dual-core ARM Cortex-M7 microcontroller (model STM32H743VIH6) with a main frequency of 480MHz, equipped with 2MB Flash and 1MB SRAM. The controller synchronously samples the DC bus 104 voltage, battery SOC, photovoltaic output current, and load power at a rate of 100ksps using a 16-bit Σ-Δ ADC (AD7768). The control algorithm adopts a five-state finite state machine model: standby, PV-priority, battery-discharge, hybrid power supply, and fault-isolation. The state switching logic is as follows: when the photovoltaic output is greater than the load demand and the battery SOC is less than 90%, it enters the PV-priority state; when the photovoltaic output is insufficient and the battery SOC is greater than 20%, it enters the battery-discharge state; when neither can meet the load demand and the SOC is between 20% and 90%, it enters the hybrid power supply state. Each state switching decision cycle is 100μs. 200μs before the switching command is issued, the controller sends a pre-trigger signal to the reverse recovery charge dynamic clamping module through the GPIO pin, so that its internal comparator and pulse generation circuit enter a high-sensitivity standby mode.

[0045] like Figure 3 As shown, during the millisecond-level seamless switching process, taking the switch from photovoltaic direct supply mode to energy storage discharge mode as an example: the central coordinating controller first shuts down the PWM output of the photovoltaic-side DC-DC converter and simultaneously starts the discharge control loop of the bidirectional DC-DC converter. At this time, the load current rapidly shifts from the photovoltaic side to the energy storage side, causing the body diode of the IGBT module 201 in the lower bridge arm of the bidirectional DC-DC converter, which was originally off, to conduct forward due to inductor freewheeling. When the next switching cycle starts, the IGBT module 201 in the upper bridge arm is triggered to conduct, forcing the body diode current of the IGBT module 201 in the lower bridge arm to reverse, entering the reverse recovery stage. During this process, the current flowing through the emitter of the IGBT module 201 in the lower bridge arm rapidly drops from +100A to -20A, and di / dt reaches -950A / μs, which is captured by the di / dt sensing unit 204. After a 30ns delay, a 100ns wide -5V negative voltage pulse is applied to the gate of the IGBT module 201 in the lower bridge arm, so that it is in a weak off state (Vge=-5V) at the initial moment of reverse recovery, thereby enhancing the electric field in the depletion region of the collector junction and accelerating the sweepout of minority carriers.

[0046] Experimental data shows that without the reverse recovery charge dynamic clamping module 203 enabled, the measured average reverse recovery charge Qrr of the FF100R12RT4 module's body diode is 112nC, and the peak reverse recovery current reaches 180A. Consequently, the voltage overshoot induced in the parasitic inductance of the power circuit (measured Lpar=50nH) is ΔV=Lpar×di / dt≈50nH×950A / μs=47.5V, accounting for 11.9% of the 400V DC bus voltage. After enabling this invention, Qrr drops to 18.3nC, the peak reverse recovery current drops to 63A, and the voltage overshoot is only 11.2V, accounting for 2.8%. In terms of switching losses, Eoff during a single commutation process decreases from 1.85mJ to 0.62mJ, a reduction of 66.5%.

[0047] To verify the long-term reliability of the system, accelerated life testing was conducted: at an ambient temperature of 85℃, the power supply mode was cyclically switched at a frequency of 10Hz under full load (50kW) for 20 hours daily. The control group used a standard -8V constant shutdown drive, while the experimental group employed the dynamic clamping mechanism of this invention. After 5000 hours of operation, the Vce(sat) drift rate of the control group IGBT module reached 8.7%, and microcracks appeared in the bond wires; the Vce(sat) drift rate of the experimental group was only 3.1%, with no visible physical damage. Based on the Arrhenius model, the mean time between failures (MTBF) of the experimental group IGBT module was 121,000 hours, while that of the control group was 52,600 hours, representing an improvement factor of 2.3.

[0048] A hard-wired synchronization interface is provided between the central coordinating controller 107 and the reverse recovery charge dynamic clamping module 203, implemented using a MAX13487EESARS485 transceiver with a transmission rate of 10Mbps. Manchester encoding is used to ensure a clock synchronization error of less than ±2ns over long distances (up to 10m). This interface is used to transmit precise timestamps of switching events, keeping the timing alignment error between clamping actions and power switching events within ±5ns. The timestamp information includes a 16-bit microsecond counter value and an 8-bit nanosecond offset, directly generated by the controller's hardware timer.

[0049] In terms of PCB layout, the power board of the bidirectional DC-DC converter 103 uses a 4-layer FR4 board with a thickness of 2.0mm. The top and bottom layers are power copper layers with a copper thickness of 70μm (2oz). The power trace width is uniformly 25mm to carry a continuous current of 200A. The loop area between the IGBT module and the DC bus support capacitor (model B43504-A9477-M, 4700μF / 450V) was optimized by three-dimensional electromagnetic field simulation and measured to be 4.7cm². The drive signal traces are arranged in the inner layer, using a microstrip line structure, with a complete ground plane as the reference plane. The trace width is 0.3mm, the distance from the reference plane is 0.2mm, and the calculated characteristic impedance is 50.2Ω. All power supply pins of driver ICs, clamping modules, and high-speed logic devices are equipped with decoupling networks: a 0.1μF C0G / NP0 ceramic capacitor (model C3216X7R1H104K) is connected in parallel with a 10μF polymer aluminum electrolytic capacitor (model 6TPE1000M), and the mounting position is no more than 4.8mm from the center of the IC pin.

[0050] All active devices in the reverse recovery charge dynamic clamping module 203 are industrial-grade wide-temperature products: the LMH7322 operates from -40℃ to +125℃, the 74LVC series logic gates from -40℃ to +125℃, and the BSS138 MOSFET from -55℃ to +150℃. The module is packaged in DFN8 (3mm×3mm) and QFN16 (4mm×4mm) packages, with thermal resistances RθJA of 45K / W and 38K / W, respectively. The bottom of the module is coated with 0.15mm thick thermal grease (thermal conductivity 3.0W / m·K) and mounted on a 5052 aluminum alloy heat sink (50mm×30mm×3mm). The heat sink is secured to the main heat sink using M3 stainless steel screws (torque 0.8N·m), and the contact thermal resistance, measured by a thermal imager, is 0.42K / W. Within an ambient temperature range of -40℃ to +85℃, the measured fluctuation range of the negative pressure pulse amplitude is -4.98V to -5.02V, and the pulse width fluctuation is 98ns to 102ns, which meets the design requirements.

[0051] The system is also equipped with an electromagnetic compatibility (EMC) filter network located between the DC bus input and the bidirectional DC-DC converter 103. This network consists of a common-mode choke (model 742792610, 1.0mH inductance), X capacitors (2 × 0.47μF, 275VAC), and Y capacitors (4 × 2.2nF, 250VAC), conforming to IEC 61000-4-5 surge immunity level 4 and CISPR 11 Class A radiated emission limits. Because this invention effectively suppresses high-frequency oscillations (mainly concentrated in the 10MHz–50MHz band) caused by the reverse recovery of the body diode, the amount of high-frequency core material used in the filter network is reduced, the common-mode inductor volume is reduced by 25%, the total capacitance of the X / Y capacitors is reduced by 30%, and the overall cost is reduced by 28%.

[0052] The technical effects of the present invention are further illustrated below through comparative data from examples and comparative cases.

[0053] The comparative implementation is as follows: the drive circuit 202 with clamping module 203 in this invention is replaced with a standard -8V turn-off drive circuit. The standard -8V turn-off drive circuit means that if the gate of the IGBT module reaches -8V, the IGBT module is turned off.

[0054] Table 1: Comparison of key performance parameters between the examples and comparative examples

[0055] As can be seen from the table above, the method of the present invention has achieved better results in terms of performance and lifespan.

[0056] In a specific implementation scenario, the microgrid is configured as follows: DC bus voltage 400V±5%, load power 30kW (resistive + inductive hybrid), photovoltaic array peak power 40kW, and energy storage battery capacity 100Ah. From 10:00 AM to 2:00 PM, photovoltaic output is sufficient (>35kW), and the system operates in photovoltaic priority mode. After 2:00 PM, cloud cover causes photovoltaic output to drop sharply to 15kW. The central coordinating controller completes the state switching decision within 100μs and activates the reverse recovery charge dynamic clamping module 200μs in advance. During the switching process, DC bus voltage fluctuations are limited to within ±1.5%, and no protective shutdown events occur. 30 consecutive days of field operation data show that the system averages 120 switching cycles per day, and the IGBT module case temperature remains stable at 78±3℃, with no heat accumulation observed.

[0057] In summary, this invention achieves hardware-level dynamic clamping of the reverse recovery charge of the body diode in the IGBT module by embedding a negative voltage gate pulse control mechanism based on real-time di / dt sensing into the drive circuit of the bidirectional DC-DC converter. This solution does not introduce additional passive buffer circuits, does not change the main power topology, and does not sacrifice the system's dynamic response speed. It can stably suppress the reverse recovery charge to below 20 nanocoulombs under typical microgrid operating conditions, simultaneously achieving multiple technical effects such as reducing switching losses, suppressing voltage oscillations, and extending the lifespan of power devices. This provides an engineering-feasible hardware implementation path for high-reliability, high-efficiency microgrid collaborative power supply systems.

[0058] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0059] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0060] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A collaborative power supply system for energy storage batteries and distributed power sources in microgrids, characterized in that, include: Energy storage battery unit, bidirectional DC-DC converter, DC bus, distributed photovoltaic power unit and central coordination controller; The energy storage battery unit is connected to the DC bus through the first power interface circuit and the bidirectional DC-DC converter, and the distributed photovoltaic power unit is connected to the DC bus through the second power interface circuit; the central coordination controller is connected to the energy storage battery unit, the bidirectional DC-DC converter and the distributed photovoltaic power unit respectively. The bidirectional DC-DC converter adopts a full-bridge topology, and its main power switching device is an IGBT module with an integrated diode package; the gate drive circuit of the IGBT module integrates a reverse recovery charge dynamic clamping module. The reverse recovery charge dynamic clamping module includes: a di / dt sensing unit, a pulse generation unit, a negative pressure injection unit, and a gate clamping execution unit; The di / dt sensing unit collects the rate of change of current flowing through the emitter of the IGBT module in real time, and triggers the pulse generation unit when the rate of change of current exceeds the set threshold. The pulse generation unit delays the generation of control pulses to control the negative pressure injection unit to switch the output voltage to the target voltage value and maintain it for a specified time; the gate clamping execution unit locks the gate potential of the IGBT module based on the target voltage value.

2. The energy storage battery and distributed power supply collaborative power supply system for microgrids as described in claim 1, characterized in that, The di / dt sensing unit includes a current acquisition component and a comparator. The current acquisition component is used to acquire the rate of change of current flowing through the emitter of the IGBT module in real time and input it into the comparator. The comparator compares the rate of change of current with a set threshold and generates an output signal based on the comparison result.

3. The energy storage battery and distributed power supply collaborative power supply system for microgrids as described in claim 2, characterized in that, The current acquisition component uses a Rogowski coil or a current transformer; a threshold setting circuit is connected to one input terminal of the comparator to provide the threshold value.

4. The energy storage battery and distributed power supply collaborative power supply system for microgrids as described in claim 1, characterized in that, The pulse generation unit is composed of a Schmitt inverter, an XOR gate, and a monostable multivibrator. The Schmitt inverter shapes the input signal of the pulse generation unit. The shaped input signal and the original input signal are input together to the XOR gate. The XOR gate generates a narrow pulse to trigger the monostable multivibrator, which outputs a control pulse after a delay time. The delay time is set by the external RC network that triggers the monostable multivibrator with the narrow pulse.

5. The energy storage battery and distributed power supply collaborative power supply system for microgrids as described in claim 1, characterized in that, The negative pressure injection unit includes a charge pump circuit, a high-speed MOSFET switch, and an energy storage capacitor. The charge pump circuit is connected to an external auxiliary power supply to power the high-speed MOSFET switch. The high-speed MOSFET switch turns on after receiving a control pulse and sends a target voltage value to the gate clamping execution unit. The energy storage capacitor is used to maintain the source voltage of the high-speed MOSFET switch.

6. The energy storage battery and distributed power supply collaborative power supply system for microgrids as described in claim 1, characterized in that, The gate clamping execution unit is composed of an N-channel MOSFET and a Schottky diode connected in parallel; the gate of the MOSFET is connected to the output terminal of the negative voltage injection unit, and the source is grounded; the drain of the MOSFET and the anode of the Schottky diode are both connected to the signal line of the drive circuit, and the cathode of the Schottky diode is connected to the target voltage value used as the reference voltage. When the negative voltage injection unit outputs the target voltage value, the MOSFET turns on, clamping the gate potential of the IGBT module to the target voltage value.

7. The energy storage battery and distributed power supply collaborative power supply system for microgrids as described in claim 1, characterized in that, A hard-wire synchronization interface is established between the central coordinating controller and the reverse recovery charge dynamic clamping module. The timestamp information of the switching event is transmitted using RS485 differential signal transmission. The timestamp includes a 16-bit microsecond counter value and an 8-bit nanosecond offset. The hard-wire synchronization interface has a transmission rate of 10 Mbps and uses Manchester encoding.

8. The energy storage battery and distributed power supply collaborative power supply system for microgrids as described in claim 7, characterized in that, The central coordinating controller adopts a dual-core ARM Cortex-M7 architecture microcontroller. Its control algorithm is based on a five-state finite state machine model, including standby, photovoltaic priority, energy storage discharge, hybrid power supply and fault isolation states. Before each state switch, a pre-trigger signal is sent to the reverse recovery charge dynamic clamping module.

9. The energy storage battery and distributed power supply collaborative power supply system for microgrids as described in claim 1, characterized in that, The PCB layout of the bidirectional DC-DC converter must meet the following conditions: the copper foil width of the power loop must be no less than 20mm, and the thickness must be 70μm; the loop area between the IGBT module and the DC bus capacitor must not exceed 5cm²; the signal lines of the IGBT module must adopt a microstrip line structure with a characteristic impedance of 50Ω and be grounded throughout; all high-frequency nodes must be equipped with a 0.1μF ceramic capacitor and a 10μF polymer capacitor connected in parallel for decoupling, and their mounting positions must be no more than 5mm from the center of the IGBT module pins.

10. The energy storage battery and distributed power supply collaborative power supply system for microgrids as described in claim 9, characterized in that, An electromagnetic compatibility (EMC) filter network is configured between the input terminal of the DC bus unit and the bidirectional DC-DC converter; the EMC filter network consists of a common-mode choke, an X capacitor, and a Y capacitor.

Images