Hybrid voltage conversion device and control method thereof

Abstract

The application discloses a hybrid voltage transformation device and a control method thereof. The hybrid voltage transformation device comprises at least one power electronic module, a controller, a communication device, a circuit breaker and a bypass circuit. The power electronic module comprises a parallel converter and a series converter which are electrically connected to form a hybrid converter, and the parallel converter is electrically connected to a low-voltage side of a distribution transformer. The controller controls signals of at least one of the first to fourth switching switches of the parallel converter and the series converter, the bypass circuit and the compensation transformer according to the number of the power electronic modules, and reduces the change of the load voltage when the voltage of the input power electronic module changes. The communication device transmits voltage and current information to the controller.

Description

Technical Field

[0001] This invention relates to a hybrid transformer device and its control method, specifically a hybrid transformer device and its control method with modular expansion capability and wattage equalization control, which can be applied to improve feeder voltage compensation capability and power supply quality. Background Technology

[0002] With the increasing proportion of renewable energy (such as solar power) generation and the widespread adoption of electric vehicles, the power quality at the end of the power grid feeders faces significant challenges. Excessive renewable energy generation can overload the grid, forcing residential solar systems to stop transmitting power or even shut down, resulting in power cuts or curtailment. Simultaneously, the high charging demand from electric vehicles can cause severe voltage drops in feeders, affecting power supply stability.

[0003] Although traditional distribution transformers are simple in structure, efficient and reliable, they are inadequate to meet these new challenges. Due to their simple function, they cannot meet the requirements of stable feeder quality and flexible regulation under the high variability of the future power grid.

[0004] Therefore, a new type of hybrid transformer and its control method are needed to solve the above problems and improve the feeder voltage compensation capability and power supply quality. Summary of the Invention

[0005] In one embodiment, the hybrid transformer device of the present invention includes: at least one power electronic module comprising: a parallel converter and a series converter electrically connected to each other to form a hybrid converter; the parallel converter being electrically connected to the low-voltage side of a distribution transformer; wherein the series converter has: a first switching switch, a second switching switch, a third switching switch, a fourth switching switch, and a compensation transformer; and a controller controlling the signals of at least one of the first switching switch, the second switching switch, the third switching switch, the fourth switching switch, a bypass circuit, and the compensation transformer of the parallel converter and the series converter according to the number of power electronic modules. Furthermore, when the voltage input to these power electronic modules changes, the load voltage variation is reduced; a communication device transmits voltage and current information of at least one of the first switching switch, the second switching switch, the third switching switch, the fourth switching switch, the bypass circuit, and the compensation transformer to the controller; and a circuit breaker is responsible for cutting off the input power source of these power electronic modules; wherein, the bypass circuit includes a relay, a silicon controlled rectifier (SCR), and a surge absorber (MOV). Through the switching speed characteristics of these components, when the hybrid converter fails, the bypass circuit achieves fault protection action, causing a short circuit on the compensation transformer side to ensure normal energy transmission.

[0006] In one embodiment, the control method of the hybrid transformer device of the present invention causes the controller included in the hybrid transformer device to perform the following steps: a voltage equalization calculation step, which uses a peak command detection method to find the maximum voltage value in the power electronic modules, and uses this as a reference command voltage for each power electronic module to follow, and obtains a voltage feedback value for each power electronic module and compares it with the reference command voltage; an undervoltage / overvoltage discrimination step, which performs calculations using the effective value of the voltage feedback value, and then performs undervoltage and overvoltage condition judgments, and adjusts the device according to the judgment result using a compensation command value; and a compensation control step, which, according to the result of the undervoltage / overvoltage discrimination step, activates the series converter and compensation control loop in each of the power electronic modules respectively.

[0007] According to the present invention, the hybrid transformer can increase the capacity and compensation range requirements through modular configuration. In addition, since the modules are equipped with watt-equalization control, the compensation output power can be evenly distributed, reducing the heavy load conditions of a single unit.

[0008] To address this issue, the hybrid transformer of this invention utilizes hybrid distribution transformer (HDT) technology, combining parallel converters with series converters to provide the power quality compensation and voltage regulation functions required by the feeder.

[0009] The hybrid transformer device of the present invention utilizes hybrid distribution transformer (HDT) technology, which integrates power electronics technology that can increase capacity with traditional transformers. It can provide the power quality compensation required by the feeder, and at the same time has the advantages of high reliability of traditional transformers and high controllability of power electronics devices. Attached Figure Description

[0010] Figure 1A This is a schematic diagram of a module circuit of one embodiment of the hybrid transformer device of the present invention.

[0011] Figure 1B This is a schematic diagram of the circuit architecture of one embodiment of the hybrid transformer device of the present invention.

[0012] Figure 2 This is a schematic diagram of the system circuit of the hybrid transformer device of the present invention.

[0013] Figure 3A This is a schematic diagram of the control flow of the hybrid transformer device and its control method of the present invention.

[0014] Figure 3B This is a timing diagram of the main voltage waveforms in the control flow of the hybrid transformer device and its control method of the present invention.

[0015] Figure 4 This is a schematic diagram of the system startup control flow of the hybrid transformer device and its control method of the present invention.

[0016] Figure 5 This is a schematic diagram of the system compensation and pressure equalization control process of the hybrid transformer device and its control method of the present invention.

[0017] Figure 6 This is a schematic diagram of the system bypass control process of the hybrid transformer device of the present invention.

[0018] Explanation of reference numerals in the attached figures:

[0019] 1: Hybrid transformer

[0020] 100: Hybrid Transformer Module

[0021] 23: Parallel Converter

[0022] 26: Series Converter

[0023] 25: DC voltage bus

[0024] Q1: First switching switch

[0025] Q2: Second switch

[0026] Q3: Third switch

[0027] Q4: Fourth switch

[0028] Q5: Fifth toggle switch

[0029] Q6: Sixth switch

[0030] Q7: Seventh toggle switch

[0031] Q8: Eighth toggle switch

[0032] A, B: Nodes

[0033] L1, L2: Inductors

[0034] I L Current

[0035] V C: Capacitor voltage

[0036] Cac: Capacitor

[0037] 27: Bypass and Surge Absorption Circuit

[0038] 101: Relay

[0039] SCR: Silicon Controlled Rectifier

[0040] MOV: Metal Oxide Rheostatist

[0041] T: Compensation Transformer

[0042] T1: First endpoint

[0043] T2: Second Endpoint

[0044] Vo1, Vo2: Primary voltage

[0045] Vo_comp1, Vo_comp2: Secondary voltage

[0046] 10,210: Distribution transformer

[0047] HV: High voltage side

[0048] LV: Low voltage side

[0049] LV1: First endpoint

[0050] N1: Second endpoint

[0051] LV2: Third endpoint

[0052] L3: Fourth endpoint

[0053] C',LV2',L3': Voltage signals

[0054] 20: Power Electronics Module

[0055] 21: Circuit breaker

[0056] 22: First connection terminal

[0057] 23': Running signal

[0058] 24: Capacitor

[0059] 28: Controller

[0060] 30: Load

[0061] F: Feeder

[0062] D: Temperature signal

[0063] L': Current signal

[0064] Q1': First switching signal

[0065] Q2': Second switching signal

[0066] Q3': Third switching signal

[0067] Q4': Fourth switching signal

[0068] 201, 202: Power Electronics Module

[0069] 231, 232: Parallel converters

[0070] 261, 262: Serial converters

[0071] 271, 272: Bypass and Surge Absorption Circuits

[0072] T, TB: Compensation Transformer

[0073] 101A, 101B: Relays

[0074] 300: Series converter control loop

[0075] 31: Compensation control loop

[0076] 32: Equalizing pressure control loop

[0077] 321A: Module

[0078] 321B: Module

[0079] S321: Voltage Equalization Calculation Steps

[0080] S322: Hysteresis Judgment Steps

[0081] S323: Undervoltage / Overvoltage Detection Procedure

[0082] 3210:Communication device

[0083] S41-S49, S51-S58, S61-S65: Steps

[0084] S1': Bypass and surge absorption circuit signal Detailed Implementation

[0085] The following describes the implementation of the present invention through specific embodiments. Those skilled in the art can understand other advantages and effects of the present invention from the content disclosed in this specification, and can therefore implement or use it through other different specific equivalent embodiments.

[0086] In one embodiment, the term "at least one" in this invention refers to one or more (e.g., one, two, or three or more), "a plurality of" refers to two or more (e.g., two, three, four, or ten or more), and "electrically connected" refers to an electrical connection or coupling, etc. However, this invention is not limited to what is mentioned in the various embodiments.

[0087] Figure 1A This is a circuit diagram of an embodiment of the hybrid transformer module in the hybrid transformer device of the present invention.

[0088] like Figure 1AAs shown, in one embodiment, the hybrid transformer module 100 of the present invention includes a parallel converter 23, a series converter 26, a bypass and surge absorption circuit 27, and a compensation transformer T, but is not limited thereto.

[0089] like Figure 1B As shown, in another embodiment, the hybrid transformer 1 may include a distribution transformer 10 and at least one power electronic module 20 that are electrically connected to each other.

[0090] In one embodiment, the distribution transformer 10 has a high-voltage side HV and a low-voltage side LV opposite to each other, and the power electronic module 20 has a parallel converter 23 and a series converter 26 electrically connected to each other, with the parallel converter 23 electrically connected to the low-voltage side LV of the distribution transformer 10.

[0091] In one embodiment, the distribution transformer 10 can be a conventional distribution transformer, a center-tapped distribution transformer, etc. The power electronic module 20 can be a power electronic circuit, a power electronic converter (such as a Heric power electronic converter), etc., the circuit breaker 21 can be a circuit breaker, etc., and the first connection terminal 22 or the second connection terminal 27 can be a connector, etc. The parallel converter 23 can be from various sources such as a solar photovoltaic (PV) converter, an energy storage device, an AC / DC converter, etc.

[0092] In one embodiment, the first terminal LV1 (e.g., the live wire terminal) and the second terminal N1 (e.g., the neutral wire terminal) of the low-voltage side LV of the distribution transformer 10 are electrically connected to the power electronic module 20, respectively. For example, the high-voltage side HV of the distribution transformer 10 may have a high voltage such as 22.8 kV, 11.4 kV, or 6.9 kV, while the low-voltage side LV of the distribution transformer 10 may have a low voltage such as 220 volts (V) or 110 volts (V).

[0093] In one embodiment, the power electronic module 20 may include a circuit breaker 21, a first connection terminal 22, a parallel converter 23, a capacitor 24, a DC voltage bus 25, a series converter 26, and a controller 28, etc., and the series converter 26 may include a first switching switch Q1, a second switching switch Q2, a third switching switch Q3, a fourth switching switch Q4, a bypass and surge absorption circuit 27, and a compensation transformer T. In one embodiment, the power electronic module 20 can be regarded as including the parallel converter 23, the capacitor 24, the DC voltage bus 25, and the series converter 26 constituting the hybrid transformer module 100, and the series converter 26 includes the surge absorption circuit 27 and the compensation transformer T.

[0094] In one embodiment, the parallel converter 23 can establish (generate) a rated DC voltage Vdc to the positive (+) and negative (-) terminals of the DC bus 25. The parallel converter 23 can be sequentially connected in parallel with the circuit breaker 21 to the low voltage side LV and feeder F of the distribution transformer 10 through the first connection terminal 22. The parallel converter 23 is also electrically connected to the capacitor 24, DC bus 25, first switching switch Q1 to fourth switching switch Q4, and controller 28 included in the series converter 26.

[0095] In one embodiment, the series converter 26 includes multiple switching switches (e.g., first switching switch Q1 to fourth switching switch Q4) for pulse width modulation (PWM) control to regulate the output voltage of the compensation transformer, thereby stabilizing the load voltage.

[0096] In one embodiment, the series converter 26 includes a capacitor 24, a first switching switch Q1, a second switching switch Q2, a third switching switch Q3, a fourth switching switch Q4, a node A, a node B, an inductor L1, an inductor L2, and a capacitor Cac.

[0097] In one embodiment, capacitor 24 may be an electrolytic capacitor or the like, storing DC energy and maintaining the voltage stability of DC voltage bus 25, which provides the DC voltage required by the series converter 26, but is not limited thereto.

[0098] In one embodiment, any of the first switching switch Q1 to the fourth switching switch Q4 may be an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), a wide bandgap (WBG) switching switch (such as a WBG MOSFET), etc.

[0099] In one embodiment, the positive terminal (+) of the DC voltage bus 25 can be electrically connected to the drain of the first switching switch Q1 and the drain of the third switching switch Q3, and the negative terminal (-) of the DC voltage bus 25 can be electrically connected to the source of the second switching switch Q2 and the source of the fourth switching switch Q4. One end of the capacitor 24 can be electrically connected to the parallel converter 23, the positive terminal (+) of the DC voltage bus 25, the drain of the first switching switch Q1 and the drain of the third switching switch Q3, respectively, and the other end of the capacitor 24 can be electrically connected to the parallel converter 23, the negative terminal (-) of the DC voltage bus 25, the source of the second switching switch Q2 and the source of the fourth switching switch Q4, respectively.

[0100] The first switch Q1 can be electrically connected to the second switch Q2 and the third switch Q3 via node A. Both the first switch Q1 and the third switch Q3 can be electrically connected to the positive terminal (+) of the parallel converter 23, the capacitor 24, and the DC voltage bus 25. The second switch Q2 can be electrically connected to the first switch Q1 and the fourth switch Q4. Both the second switch Q2 and the fourth switch Q4 can be electrically connected to the negative terminal (-) of the parallel converter 23, the capacitor 24, and the DC voltage bus 25. For example, the source of the first switch Q1 can be electrically connected to the drain of the second switch Q2, the drain of the first switch Q1 can be electrically connected to the drain of the third switch Q3, the source of the second switch Q2 can be electrically connected to the source of the fourth switch Q4, and the source of the third switch Q3 can be electrically connected to the drain of the fourth switch Q4 via node B. The first switch Q1 to the fourth switch Q4 can form an H-bridge switch structure.

[0101] In one embodiment, the first switching switch Q1 to the fourth switching switch Q4 constitute an H-bridge switching structure, and the output is adjusted by pulse width modulation (PWM) control through switching action.

[0102] In one embodiment, the output current I is via node A. L One end of inductor L1 is connected to the other end of inductor L1, which is connected to the first terminal T1 of compensation transformer T, but not limited thereto.

[0103] In one embodiment, one end of inductor L2 is connected to node B, and the other end of inductor L2 is connected to the second terminal T2 of compensation transformer T, but is not limited thereto.

[0104] The two ends of capacitor Cac can be electrically connected to the other ends of inductors L1 and L2, respectively. One end of capacitor Cac can be electrically connected to the second end of inductor L1 and the first terminal T1 of compensation transformer T, and the other end of capacitor Cac can be electrically connected to the other end of inductor L2 and the second terminal T2 of compensation transformer T. That is, the other ends of the two inductors L1 and L2 can first be connected in parallel to the two ends of capacitor Cac, and then electrically connected to the first terminal T1 and the second terminal T2 of compensation transformer, respectively.

[0105] like Figure 1AAs shown, in one embodiment, the bypass and surge absorption circuit 27 includes a relay 101, a silicon controlled rectifier (SCR), and a metal oxide varistor (MOV). The primary function of the bypass and surge absorption circuit 27 is to provide bypass functionality and protection, but it is not limited thereto.

[0106] In one embodiment, relay 101 is a switching element that controls the bypass function. When bypassing the series converter is required, relay 101 is closed, allowing current to flow directly through the bypass circuit, but this is not the only embodiment.

[0107] In one embodiment, the silicon controlled rectifier (SCR) and the metal oxide varistor (MOV) constitute a surge protection circuit. When a surge voltage occurs in the circuit, the SCR is turned on, and the surge current is introduced into the MOV for absorption. The MOV can absorb the surge voltage, protect the circuit components, and thus protect the downstream circuit, but is not limited to this.

[0108] In one embodiment, the controller 28 may be a microcontroller unit (MCU) or the like, and the feeder F may be a power line, distribution line, transmission line, or the like.

[0109] In one embodiment, the two ends of the circuit breaker 21 of the power electronic module 20 can be connected in parallel to the first terminal LV1 (such as the live wire terminal) and the second terminal N1 (such as the neutral wire terminal) of the low voltage side LV of the distribution transformer 10, respectively. The two ends of the first connection terminal 22 can be electrically connected to the two ends of the circuit breaker 21, and the circuit breaker 21 can be electrically connected in sequence to the first connection terminal 22 and the parallel converter 23.

[0110] In one embodiment, the first terminal T1 of the compensation transformer T is electrically connected to the second side of the inductor L1 and one end of the capacitor Cac, and the second terminal T2 of the compensation transformer T is electrically connected to the second side of the inductor L2 and the other end of the capacitor Cac. The third terminal LV2 of the compensation transformer T is electrically connected to the first terminal LV1 of the low-voltage side LV of the distribution transformer 10 via feeder F, and the fourth terminal L3 of the compensation transformer T and the second terminal N1 of the low-voltage side LV of the distribution transformer 10 are respectively electrically connected to the two ends of the load 30 via feeder F. That is, the first terminal LV1 of the low-voltage side LV of the distribution transformer 10 is electrically connected to the third terminal LV2 of the compensation transformer T, and the output terminals of the hybrid transformer device 1 are electrically connected to the four terminal L3 of the compensation transformer T and the second terminal N1 of the low-voltage side LV of the distribution transformer 10 to the two ends of the load 30.

[0111] The controller 28 can be electrically connected to the parallel converter 23, the DC voltage bus 25, the first switching switch Q1 to the fourth switching switch Q4 and the bypass and surge absorption circuit 27, etc. The controller 28 can generate the first switching switch signal Q1' to the fourth switching switch signal Q4' and the bypass and surge absorption circuit signal S1', respectively, to control the first switching switch Q1 to the fourth switching switch Q4 and the bypass and surge absorption circuit 27.

[0112] The controller 28 can receive the operating signal 23' (such as a normal circuit feedback signal) of the parallel converter 23 to monitor whether the parallel converter 23 is operating normally (such as whether any abnormal state has occurred) based on the operating signal 23'. The controller 28 can also monitor whether the parallel converter 23 has established a rated DC voltage (such as a DC voltage of 380 or 400 volts) to the positive (+) and negative (-) terminals of the DC voltage bus 25. The controller 28 can receive the voltage signal C' of the capacitor Cac, the voltage signal LV2' of the feeder F before adjustment (such as the voltage between the third terminal LV2 of the compensation transformer T and the second terminal N1 of the low voltage side LV of the distribution transformer 10), the voltage signal L3' of the feeder F after adjustment (such as the voltage between the fourth terminal L3 of the compensation transformer T and the second terminal N1 of the low voltage side LV of the distribution transformer 10), the current signal L' of the inductors L1 and L2, and the temperature signal D of the series converter 26 (such as at least one of the first switching switch Q1 to the fourth switching switch Q4 and the bypass and surge absorption circuit 27).

[0113] Figure 2 This is a schematic diagram of the system circuit of the hybrid transformer device of the present invention.

[0114] Figure 2 In this system, the hybrid transformer adopts a modular control strategy, allowing at least two power electronic modules to operate in series to improve system capacity and reliability.

[0115] In one embodiment, the distribution transformer 210 is connected to the grid voltage VGrid on one side and to the power supply voltage VSource on the other side, but is not limited thereto.

[0116] As shown in the figure, the system circuit forms a series compensation. The compensation transformer TB of the power electronic module 201 and the compensation transformer TB of the power electronic module 202 are connected in series and share the same output current. The output voltage of each module is automatically adjusted according to the feeder voltage requirements.

[0117] The control method of this invention employs watt-equalizing control, which distributes the load evenly among the power electronic modules, thereby improving system efficiency and lifespan. In one embodiment, series watt-equalizing control is used, where the controller 28 adjusts the PWM control signal according to the output voltage of each power electronic module 201, 202, so that the output power of each module is evenly distributed.

[0118] More specifically, power electronic module 201 includes a parallel converter 231, a series converter 261, a bypass and surge absorption circuit 271, and a compensation transformer TB; power electronic module 202 includes a parallel converter 232, a series converter 262, a bypass and surge absorption circuit 272, and a compensation transformer TB.

[0119] In one embodiment, one end of the secondary side of the compensation transformer TB of the power electronic module 201 is connected to the power supply voltage VSource, and the other end of the secondary side of the compensation transformer TB of the power electronic module 201 is connected to one end of the secondary side of the compensation transformer TB of the power electronic module 202, forming a series structure. The other end of the secondary side of the compensation transformer TB of the power electronic module 202 outputs the load voltage V. LOAD However, it is not limited to this.

[0120] In one embodiment, the series converters 261 and 262 include first switching switches Q1 to fourth switching switches Q4 and fifth switching switches Q5 to eighth switching switches Q8 for pulse width modulation (PWM) control to adjust the output voltage of the compensation transformer TB of power electronic module 201 and the compensation transformer TB of power electronic module 202, thereby stabilizing the load voltage V. Load The output of series converter 261 is connected to the primary side of the compensation transformer TB of power electronic module 201; the output of series converter 262 is connected to the primary side of the compensation transformer TB of power electronic module 202.

[0121] The secondary windings of the compensation transformers TB of power electronic module 201 and TB of power electronic module 202 are connected in series on the feeder to compensate for the feeder voltage drop. The compensation transformers TB of power electronic module 201 and TB of power electronic module 202 are connected in series and share the same output current. The output voltage of each module is automatically adjusted according to the feeder voltage requirement to jointly maintain the load voltage V. Load Stablize.

[0122] In one embodiment, power electronic modules 201 and 202 further include bypass and surge absorption circuits 271 and 272 for providing bypass functionality and protection. When a power electronic module fails or requires maintenance, it can be isolated through the bypass function, while other modules can continue to operate, ensuring the reliability of power supply.

[0123] The above configuration can effectively improve system capacity, reliability and efficiency, and is applicable to various power distribution systems to enhance the grid connection stability of renewable energy, improve the charging efficiency of electric vehicles, stabilize feeder voltage and reduce power loss.

[0124] Figure 3A This is a schematic diagram of the control flow of the series converter control loop 30 in the hybrid transformer of the present invention.

[0125] Taking two modules as an example, the feedback voltage information of each module is exchanged through communication or analog signals, and the controller of each module compares the maximum value as a reference command, which is then sent to the overall process of the control loop of each module.

[0126] Figure 3A In the control flow shown, the series converter control loop 300 mainly includes two loops: a compensation control loop 31 and a voltage equalization control loop 32. In one embodiment, the series converter control loop 30 is responsible for controlling the output voltage and current of the series converter to achieve the required voltage compensation effect.

[0127] In one embodiment, the compensation control loop 31 receives the load voltage reference value V_Load_rms_ref* as input, adds it to the output of the voltage equalization control loop 32 via an adder, and subtracts the effective value V of the load voltage via a subtractor. Lord_rms The voltage compensation value is generated by a proportional-integral controller (PI), then the phase of the compensation value is adjusted by a sine wave generator (Sinθ) via a multiplier, and the resulting capacitor voltage reference value V is obtained. C_ref* Subtract the capacitor voltage V using a subtractor. C Then input to the proportional controller P to obtain I. L_ref *Inductor current reference value, subtracted from inductor current I by a subtractor. L The inductor current output value I is obtained through a proportional-integral controller (PI). L_Out Through the adder and the feedback voltage V ff The values ​​are added together, where the feedback voltage Vff is obtained by dividing the capacitor voltage Vc by the DC voltage Vdc, and the inductor current output value I is calculated. L_Out With feedback voltage V ff The summed output is used as the output of the PWM generator (PWMGen) to generate PWM control signals for the first switching switch Q1 to the fourth switching switch Q4.

[0128] In one embodiment, the equalization control loop 32 is responsible for balancing the output power of each module to improve system efficiency and extend module life.

[0129] In one embodiment, the equalization control loop 32 sequentially performs the following steps:

[0130] Voltage equalization calculation step S321: Receive feedback voltage information from each module 321A, 321B (e.g., the secondary voltage Vo_comp1, Vo_comp2 or primary voltage Vo1, Vo2 of the compensation transformer TB of power electronic module 201 and the compensation transformer TB of power electronic module 202) via communication or analog signals transmitted to controller 28, and use the maximum value selector Max to compare and obtain the maximum value as the effective value of the command voltage qVcom_rms. Then, subtract the feedback value of the other corresponding module to calculate the error signal qV_com_err, and input it to the proportional-integral controller PI to generate the control signal qV_com_out based on the error signal.

[0131] Hysteresis judgment step S322: The control signal qV_com_out is used as the input to the hysteresis judgment step S322 and output to the undervoltage / overvoltage judgment step S323.

[0132] Undervoltage / overvoltage detection step S323: The output voltage of the module is monitored by the undervoltage / overvoltage detection step S323. If the voltage exceeds the preset safety range, a protection mechanism will be triggered, such as stopping the module operation. In one embodiment, the output of the undervoltage / overvoltage detection step S323 is used as the output of the voltage equalization control loop to ensure that the output voltage of each module is within the safety range and to improve system stability.

[0133] Here, the master-servant control primarily utilizes communication or analog signals to exchange compensation voltage information between modules. Taking two modules as an example, the voltage equalization control loop 32 will chase the higher compensation voltage value. If the maximum value chased exceeds the average voltage, the total compensation voltage will exceed the target value. The excess will be corrected by the compensation control loop 31. Therefore, the voltage equalization control loop 32 will cause the compensation voltage difference between modules to converge and eventually catch up with the average voltage value. With this configuration, even in the case of multiple modules or when some modules are in bypass mode, the voltage equalization control loop 32 can achieve voltage equalization control.

[0134] Figure 3B This is a timing diagram of the main voltage waveforms in the control flow of the hybrid transformer device and its control method of the present invention.

[0135] In one embodiment, as shown in the figure, two modules S1 and S2 are connected in series for compensation. During time points t0-t1, neither power electronic module 201 nor power electronic module 202 (hereinafter also referred to as modules S1 and S2) performs compensation. Module S1 short-circuits the transformer using a circuit switch, and module S2 short-circuits the transformer using a bypass switch. During time points t1-t2, module S1 begins to compensate, and the load voltage is compensated from, for example, 200V to 208V. During time points t2-t3, module S2 also begins to compensate, and the load voltage is subsequently compensated from, for example, 208V to 216V. Here, it can be seen that both modules perform compensation after time point t3, so it can be seen from the waveforms Vo_S1 and Vo_S2 that the compensation voltages of the two modules are the same, achieving the effect of voltage equalization control.

[0136] Figure 4 This is a schematic diagram of the system startup control flow of the hybrid transformer device and its control method of the present invention.

[0137] As shown in the figure, the system startup control process includes the following steps:

[0138] Step S41: First, start the module.

[0139] Step S42: After starting the module, short-circuit the silicon controlled rectifier (SCR) to close the relay, allowing current to flow through the bypass circuit and ensuring system safety.

[0140] Step S43: Detect fault signals such as DC bus voltage, power supply voltage (Vsource), and metal oxide rheostat (MOV). If an abnormality (N) is detected, return to step S42; if normal (Y) is detected, proceed to step S44.

[0141] Step S44: Start the parallel converter with the goal of establishing the DC bus voltage to a predetermined voltage (e.g., 400V), then proceed to step S45.

[0142] Step S45: Determine if the DC bus voltage is greater than the predetermined voltage (e.g., 400V). If the voltage is insufficient (N), return to step S44 and continue waiting; if the voltage has reached the predetermined voltage (Y), proceed to the next step S46.

[0143] Step S46: Start the series converter and compensation control circuit. The initial compensation voltage target is set to 0V for example. Start controlling the switching of the first switching switch Q1 to the fourth switching switch Q4. At the same time, short-circuit the silicon controlled rectifier SCR and disconnect the relay to allow current to flow through the series converter for voltage compensation.

[0144] Step S47: Determine if it is a phase zero. If it is not a phase zero (N), return to step S46 and continue waiting; if it is a phase zero (Y), proceed to the next step S48.

[0145] Step S48: Perform over / under voltage compensation, set the target voltage to the target value (e.g., 220V), and start a soft start to allow the voltage to rise smoothly to the target value, then proceed to the next step S49.

[0146] Step S49: End.

[0147] Through the above process, the present invention can effectively start the hybrid transformer device and ensure that the system operates in a safe and stable state, while achieving precise voltage compensation function and improving power supply quality.

[0148] Figure 5 This is a schematic diagram of the system compensation and pressure equalization control process of the hybrid transformer device and its control method of the present invention.

[0149] As shown in the figure, the system compensation and pressure equalization control process includes the following steps:

[0150] Step S51: First, start the series compensation control and voltage equalization control, and proceed to the next step S52.

[0151] Step S52: Collect the compensation voltage of each module through communication or analog signals.

[0152] Step S53: Perform voltage equalization calculation, for example, compare the compensation voltage of each module and select the maximum value as the reference command.

[0153] Step S54: Check the load voltage V LOAD Check if it exceeds the preset hysteresis range, for example, 220Vrms ± 0.5%. If it exceeds the range (N), proceed to step S55B; if it is within the range (Y), proceed to step S55A.

[0154] Step S55A: Set the equalization compensation to 0 and proceed to the next step S56.

[0155] Step S55B: Perform over / under voltage compensation judgment to determine whether the power supply voltage (Vsource) is higher than 220Vrms. If yes (Y), set the compensation direction to -1 and proceed to step S55B2; if no (N), proceed to the next step S56.

[0156] Step S56: Execute the compensation control loop and proceed to the next step S57.

[0157] Step S57: Generate PWM control signals for the first switching switch Q1 to the fourth switching switch Q4 to drive the series converter to perform voltage compensation, and proceed to the next step S58.

[0158] Step S58: End.

[0159] Through the above process, the present invention can effectively coordinate the operation of multiple power electronic modules, achieve precise voltage compensation and load balancing, and improve system efficiency, stability and module lifespan.

[0160] Figure 6 This is a schematic diagram of the system bypass control process of the hybrid transformer device of the present invention.

[0161] As shown in the figure, the system bypass control process includes the following steps:

[0162] Step S61: First, start the bypass process and proceed to the next step S62.

[0163] Step S62: Perform series compensation and voltage equalization control, be ready to put the system into bypass mode at any time, and proceed to the next step S63.

[0164] Step S63: Determine whether the system's automatic reset protection has been triggered. If not (N), return to step S62; if yes (Y), proceed to step S64.

[0165] Step S64: Perform the following actions: shut down the series converter and the parallel converter, stop voltage compensation and power supply; short-circuit the silicon controlled rectifier (SCR) to allow current to flow directly through the bypass circuit; close the relay to further ensure the bypass circuit is open; close the second switching switch Q2 and the fourth switching switch Q4 to provide an additional bypass path; open the first switching switch Q1 and the third switching switch Q3 to isolate the series converter and avoid interference with the bypass circuit; proceed to the next step S65.

[0166] Step S65: End.

[0167] With the above configuration, when the system malfunctions, the present invention can activate the bypass function to protect the system and maintain basic power supply.

[0168] The above embodiments are merely illustrative of the principles, features, and effects of the present invention and are not intended to limit the scope of implementation of the present invention. Any person skilled in the art can modify and alter the above embodiments without departing from the spirit and scope of the present invention. Any equivalent changes and modifications made using the content disclosed in this invention should still be covered by the claims. Therefore, the scope of protection of this invention should be as listed in the claims.

Claims

1. A hybrid transformer, comprising: At least one power electronic module, including: A parallel converter and a series converter are electrically connected to each other to form a hybrid converter. The parallel converter is electrically connected to the low-voltage side of a distribution transformer. The serial converter has the following features: A first switching switch, a second switching switch, a third switching switch, a fourth switching switch, and a compensation transformer; A controller controls the signals of at least one of the first switching switch, the second switching switch, the third switching switch, the fourth switching switch, a bypass circuit, and the compensation transformer of the parallel converter and the series converter according to the number of power electronic modules, and reduces the change in load voltage when the voltage input to the power electronic modules changes. A communication device transmits voltage and current information of at least one of the first switching switch, the second switching switch, the third switching switch, the fourth switching switch, the bypass circuit, and the compensation transformer to the controller; and A circuit breaker is responsible for cutting off the power source of these power electronic modules; The bypass circuit includes a relay, a silicon controlled rectifier (SCR), and a surge absorber (MOV). Through the switching speed characteristics of these components, when the hybrid converter fails, the bypass circuit performs a fault protection action, causing a short circuit on the compensation transformer side to ensure normal energy transmission.

2. The hybrid transformer as described in claim 1, wherein, The bypass circuit performs short-circuit behavior on the compensation transformer. The controller monitors the voltage of the hybrid converter and determines whether an abnormality has occurred. When an abnormality that can be regarded as a fault is determined, the controller closes at least one of the switches of the bypass circuit to bypass the hybrid converter.

3. The hybrid transformer device of claim 1, wherein the hybrid transformer further includes a sensor and a monitoring device for monitoring the operation of the hybrid transformer, the monitoring device being connected to the one or more tapped conventional transformers.

4. The hybrid transformer device as described in claim 1 or 2, wherein the switching element of the bypass circuit receives commands issued by the controller and, in conjunction with the start and stop procedure flow of the controller, performs bypass or high-frequency switching of the switch.

5. The hybrid transformer as described in claim 1, wherein, The power electronic module also has a first connection terminal, the two ends of the circuit breaker are respectively connected in parallel to the first end and the second end of the low voltage side of the distribution transformer, the two ends of the first connection terminal are respectively electrically connected to the two ends of the circuit breaker, and the circuit breaker is sequentially electrically connected to the first connection terminal and the parallel converter.

6. The hybrid transformer as claimed in claim 1, wherein, The power electronic module also has a DC voltage bus and a first connection terminal. The parallel converter establishes a rated DC voltage to the positive and negative terminals of the DC voltage bus. The parallel converter is sequentially connected in parallel with the circuit breaker through the first connection terminal to the low voltage side and feeder of the distribution transformer. The parallel converter is also electrically connected to the first connection terminal, the DC voltage bus and the series converter.

7. The hybrid transformer as claimed in claim 1, wherein, The power electronic module also has a DC voltage bus, the positive terminal of which is electrically connected to the drain of the first switch and the drain of the third switch, and the negative terminal of which is electrically connected to the source of the second switch and the source of the fourth switch.

8. The hybrid transformer as claimed in claim 1, wherein, The source of the first switching switch is electrically connected to the drain of the second switching switch, the drain of the first switching switch is electrically connected to the drain of the third switching switch, the source of the second switching switch is electrically connected to the source of the fourth switching switch, the source of the third switching switch is electrically connected to the drain of the fourth switching switch, and the first switching switch to the fourth switching switch form an H-bridge switch structure.

9. The hybrid transformer as claimed in claim 1, wherein, The power electronic module also has a DC voltage bus. The controller receives the operating signal of the parallel converter to monitor whether the parallel converter is operating normally based on the operating signal, and the controller monitors whether the parallel converter has established a rated DC voltage to the positive and negative terminals of the DC voltage bus.

10. A method for controlling a hybrid transformer, wherein the controller included in the hybrid transformer as claimed in claim 1 is caused to perform the following steps: The voltage equalization calculation step uses the peak command detection method to find the maximum voltage in these power electronic modules, which is used as the reference command voltage for each power electronic module to follow, and obtains the voltage feedback value for each power electronic module and compares it with the reference command voltage. The undervoltage / overvoltage discrimination step involves calculating the effective value of the voltage feedback value, then determining undervoltage and overvoltage conditions, and adjusting the compensation command value based on the judgment result; and The compensation control step, based on the result of the undervoltage / overvoltage discrimination step, activates the series converter and compensation control loop in each of the power electronic modules.

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