An equivalent synchronous boost control method for an electrically excited doubly salient motor

Abstract

The embodiment designs an equivalent synchronous boost control method for an electrically excited doubly salient motor, and belongs to the technical field of variable reluctance motor control. In the application, a DSP generates an excitation control signal and a unified boost control signal according to a DC bus voltage and an excitation current, and an FPGA filters and determines the direction of three-phase currents; when the unified boost control signal is at a high level, the three-phase upper bridge arm switching devices are controlled to be simultaneously turned on to form an equivalent boost state; when the unified boost control signal is at a low level, the corresponding bridge arm switching devices are controlled to be turned on according to the direction of each phase current to realize synchronous rectification. The method does not need a rotor position sensor and an additional voltage detection circuit, can reduce the controller loss, and improve the output capacity and efficiency of the electrically excited doubly salient motor power generation system under high-speed working conditions.

Description

Technical Field

[0001] This invention relates to the field of variable reluctance motor power generation control technology, and in particular to an equivalent synchronous boost control method for electrically excited doubly salient pole motors. Background Technology

[0002] With the rapid development of more-electric aircraft technology, the electrification level of airborne secondary energy systems is constantly improving. The integrated starter / generator system, as an important component of the airborne electrical system, combines engine starting and airborne power supply functions. It boasts advantages such as small size, light weight, high power density, flexible control, and ease of system integration, thus becoming one of the key devices in the energy systems of more-electric aircraft.

[0003] Electrically excited doubly salient pole motors are a type of special motor suitable for integrated starter / generator applications. These motors employ a brushless structure, with both the stator and rotor constructed from stacked silicon steel sheets. The rotor lacks permanent magnets and windings; its internal magnetic field is established by an independent excitation winding. This results in a robust structure, adjustable excitation, high reliability, and suitability for high-speed operation. In integrated starter / generator applications, electrically excited doubly salient pole motors typically use a bidirectional converter as the controller, achieving a high degree of system integration. During starter operation, the bidirectional converter functions as an inverter; during generator operation, it functions as a rectifier. During generator operation, when control relies on rotor position information, metal-oxide-semiconductor field-effect transistors (MOSFETs) can be used to achieve controlled rectification. Furthermore, utilizing the body diode of the MOSFET can form a diode rectifier, enabling uncontrolled rectification control independent of rotor position information.

[0004] However, existing rectification control methods all have certain limitations under high-speed power generation conditions. For controlled rectification, the resolution of position signals output by position sensors such as rotary transformers is limited at high speeds, increasing detection errors. This makes it difficult to accurately adjust the conduction position of the controlled rectifier based on rotor position information, thus affecting control performance and system stability. For uncontrolled rectification, on the one hand, as output power increases, the amplitude of motor phase current increases, while the body diode of MOSFETs typically has a high forward voltage drop, leading to a significant increase in conduction losses. Controller losses and heat generation rise rapidly, affecting the efficiency and thermal reliability of the power generation system. On the other hand, uncontrolled rectification cannot fully utilize the advantages of controlled rectification in terms of output capacity improvement and excitation optimization. Under high-speed conditions, it may also cause problems such as increased iron losses and exacerbated DC bias effects, further reducing the overall efficiency of the power generation system.

[0005] Therefore, how to achieve controllable rectification control suitable for high-speed operation under sensorless conditions, while simultaneously suppressing controller losses, has become a key technical problem that urgently needs to be solved in electrically excited doubly salient pole generator systems. Synchronous rectification control technology is a common technique in power electronics to reduce rectification losses. Its basic principle is to control the synchronous conduction of the corresponding MOSFET during the conduction period of the MOSFET body diode, so that the current preferentially flows through the path with lower on-state voltage, thereby reducing conduction losses. The boost control circuit increases the output voltage or output capacity by controlling the on / off state of the power supply and the inductor branch, utilizing the energy stored in the inductor and the energy released by the capacitor. For the generator system of an electrically excited doubly salient pole motor, its generator operation circuit has similar topological characteristics to the synchronous boost converter circuit, and it has the potential to improve the generator output capacity and reduce controller losses through equivalent synchronous boost control. However, there are currently no relevant documents or patents that have studied the equivalent method.

[0006] In summary, how to further optimize the equivalent synchronous boost control method of electrically excited doubly salient pole motors to reduce controller losses and improve the efficiency of the power generation system has become a research topic. Summary of the Invention

[0007] The embodiments of the present invention provide an equivalent synchronous boost control method for an electrically excited doubly salient pole motor, which can reduce controller losses and improve the efficiency of the power generation system in the equivalent synchronous boost control of the electrically excited doubly salient pole motor.

[0008] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0009] An equivalent synchronous boost control method for an electrically excited doubly salient pole motor is disclosed. This method is applied to a power generation system including the electrically excited doubly salient pole motor. The power generation system includes: the electrically excited doubly salient pole generator, a three-phase full-bridge controllable rectifier, an excitation power supply unit, a DC bus capacitor, a load, a sampling circuit, a digital signal processor (DSP), and a field-programmable gate array (FPGA). The electrically excited doubly salient pole motor is in generator operation, driven by an external prime mover. The generated AC power is rectified by the three-phase full-bridge controllable rectifier and output to the DC bus to power the load. The excitation winding is powered by an independent excitation power supply.

[0010] The method includes:

[0011] S1. Acquire the actual three-phase current and excitation current of the electrically excited doubly salient pole motor. This can be achieved using a current sensor to acquire the three-phase current and excitation current, and a voltage sensor to acquire the DC bus voltage. The analog signals are converted into digital signals by a conditioning circuit and then sent to the DSP and FPGA respectively. Specifically, the bus voltage and excitation current employ a closed-loop regulation control system consisting of an outer loop for bus voltage and an inner loop for excitation current. The current is sampled using a Hall effect sensor.

[0012] S2. Based on the deviation between the excitation current reference value and the actual excitation current, PI regulation is performed. Specifically, the digital signal processor (DSP) performs proportional-integral (PI) regulation based on the deviation between the given DC bus voltage and the sampled actual DC bus voltage to generate the excitation current reference value. Then, based on the deviation between the excitation current reference value and the actual excitation current, PI regulation is performed again to output the excitation winding control signal, thereby achieving stable bus voltage control. Specifically, the DSP generates a unified boost switching signal required for synchronous boost control based on the current operating conditions, and can set the corresponding duty cycle according to different operating conditions.

[0013] S3. After filtering the actual three-phase currents, the phase current direction is determined. Considering the sampling noise and current ripple near the zero-crossing point of the three-phase current under high-speed operating conditions, the FPGA first performs digital filtering on the acquired three-phase current signals to improve the reliability of current direction determination. Specifically, a digital moving average filtering method can be used to reduce jitter errors near the zero-crossing point. The filtered phase current signal is used as the input for subsequent current direction determination.

[0014] S4. When the unified boost switch signal is at a high level, the phase current amplitude is increased through boost control. It should be noted that the high level and low level in this embodiment are not specific values, but two relative concepts. They are distinguished by enabling and disabling. For example, a high level corresponds to enabling and is considered as 1; a low level corresponds to disabling and is considered as 0.

[0015] S5. When the unified boost switch signal is at a low level, the corresponding bridge arm is assigned a synchronous rectification turn-on signal according to the determination result of the phase current direction. In the non-boost interval, the freewheeling path is undertaken by the MOSFET.

[0016] Optionally, during the execution of S1-S5, the current waveform can be recorded in real time and the conduction loss and switching loss can be calculated. The recorded data is written into the operation log of the power generation system.

[0017] Specifically, S3 includes: the FPGA comparing the filtered current value of each phase with preset positive and negative current conduction thresholds. When the current of a phase is greater than the positive threshold, the current direction of that phase is determined to be positive; when the current of a phase is less than the negative threshold, the current direction of that phase is determined to be negative; when the current of a phase is between the positive and negative thresholds, it is determined to be in an uncertain region near the zero crossing point, and synchronous rectification is not triggered in this case to avoid false turn-on. The positive and negative current conduction thresholds are set to 5~20A depending on the rotational speed. By setting the above positive and negative thresholds, the misjudgment problems caused by sampling noise, ripple, and commutation overlap under high-speed operation conditions can be effectively suppressed.

[0018] S4 includes: When the unified boost switch signal is high, it controls the simultaneous conduction of the three-phase upper bridge arm MOSFETs and the turn-off of all lower bridge arm switches. At this time, the motor windings store energy, and the three-phase full-bridge controllable rectifier is equivalent to the boost switch conduction state in a synchronous boost circuit. During the high-level interval, the load is mainly powered by the DC bus capacitor, and the motor winding current rapidly increases, forming a boost effect and improving the subsequent output capability. Taking phase A current as positive and phases B and C current as negative as an example, the current amplitude under boost control and uncontrolled rectification is as follows: , where i p-Boost For the phase current amplitude under boost control, i p-DR To control the phase current amplitude under uncontrolled rectification, i a Let e ​​be the phase A current. a , e b , e c The electromotive forces of the three-phase windings A, B, and C are respectively, r p u is the equivalent resistance of the phase winding. DC This refers to the bus voltage. Boost control can effectively increase the phase current amplitude.

[0019] In S5, the comparison method for the current of a phase includes: when the unified boost switch signal is low, the system enters the non-boost interval. At this time, based on the phase current direction determination result obtained in step five, synchronous rectification turn-on signals are assigned to each phase arm. Specifically, when the current direction of a phase is positive, the upper bridge arm switch of that phase is turned on; when the current direction of a phase is negative, the lower bridge arm switch of that phase is turned on; when a phase is in the uncertain interval near zero crossover, both the upper and lower bridge arms of that phase remain off, allowing the anti-parallel diode to naturally freewheel or wait for the next stable determination interval. This achieves the following: in the non-boost interval, the freewheeling path originally undertaken by the body diode is now undertaken by the MOSFET with a lower on-state voltage drop, thereby reducing conduction losses and achieving synchronous rectification. The formulas for calculating the conduction losses of MOSFETs and diodes, as well as the switching losses of MOSFETs, are as follows: , where P cond-MOS , Pcond-D and P switch-MOS These represent the conduction losses of the MOSFET and diode, respectively, as well as the switching losses of the MOSFET. V ON-MOS and V ON-D These are the forward voltage drops of the MOSFET and the diode, respectively, and are respectively quantized by the current i flowing through the MOSFET. x-MOS and the current i flowing through the diode x-D Decision. s E is the switching frequency. ON and E OFF This refers to the energy required for the MOSFET to turn on and off. It is determined by the current at the instants of turn-on and turn-off, i. x-ON and i x-OFF Decision. Due to V ON-MOS Much smaller than V ON-D Using MOSFETs instead of diodes for conduction can significantly reduce the conduction loss of the controller.

[0020] Furthermore, to ensure control safety, after the FPGA generates the synchronous boost turn-on signal and the synchronous rectification turn-on signal, protection logic is added, including: shoot-through protection for the upper and lower transistors of the same bridge arm and overcurrent protection. The dead time includes measures to prevent shoot-through faults caused by overlapping drive switching of the upper and lower switching devices in the same bridge arm. Dead time refers to the time that must be set when adjacent switching devices are turned on; its function is to prevent a short circuit caused by the following switching device starting to turn on before the previously turned-on switching device has completely turned off. For example, if the upper transistor of phase A turns on and the lower transistor of phase A needs to follow, a dead time is needed between the two conduction intervals for a safety gap. The overcurrent protection includes shutting off the corresponding drive signal when the phase current exceeds a set threshold. After the above processing, the final gate drive signal is output to the three-phase full-bridge controllable rectifier, completing the implementation of the equivalent synchronous boost control method of this invention. For example, if the FPGA receives a DSP signal and determines that both the upper and lower transistors of the same phase have turn-on signals, it makes a logical judgment that conduction cannot proceed at this time, forming a double insurance with the dead time.

[0021] The equivalent synchronous boost control method for electrically excited doubly salient pole motors provided in this invention is applicable to the control of electrically excited doubly salient pole motors under high-speed, sensorless power generation conditions. In this embodiment, a three-phase full-bridge controllable rectifier is equivalent to a synchronous boost circuit, enabling the power generation system to improve phase current build-up capability and output performance under high-speed, heavy-load conditions through unified boost control. Simultaneously, synchronous rectification is implemented based on the phase current direction in the non-boost control range, shifting the freewheeling path from the body diode to the MOSFET, thereby effectively reducing controller conduction losses. Since it does not rely on a rotor position sensor and requires no additional voltage detection circuit, it is suitable for high-speed, sensorless power generation conditions, which helps improve the efficiency of the power generation system, especially significantly improving output capability and reducing total losses under high-speed, heavy-load conditions. Also, because it does not rely on a rotor position sensor and requires no additional voltage detection circuit, this solution requires fewer sensors and circuit components compared to existing technologies, resulting in a lower failure rate and higher reliability. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A system structure block diagram of an equivalent synchronous boost control method for an electrically excited doubly salient pole motor provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram illustrating the principle of the three-phase full-bridge controllable rectifier power generation system in this invention as equivalent to a synchronous boost circuit;

[0025] Figure 3 This is a schematic diagram of the conduction scheme for the equivalent synchronous boost control method of the present invention;

[0026] Figure 4 This is a schematic diagram and a judgment process for determining the conduction of a switching transistor based on a current threshold during the synchronous rectification process of the present invention.

[0027] Figure 5 The waveform diagram shows the experimental results of the equivalent synchronous boost control method for electrically excited doubly salient pole motors proposed in this invention.

[0028] Figure 6 This invention presents a comparison of the equivalent synchronous boost control method for electrically excited doubly salient pole motors proposed in this invention with the controller losses of traditional uncontrolled rectifiers.

[0029] Figure 7The efficiency distribution of the equivalent synchronous boost control method for electrically excited doubly salient pole motors proposed in this invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Embodiments of the present invention will be described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in the specification of the present invention means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0031] like Figure 1 The diagram shows the overall structure of an equivalent synchronous boost control system for an electrically excited doubly salient pole motor according to the present invention. The controlled object is a high-speed electrically excited doubly salient pole motor, whose three-phase armature windings are connected in a star configuration. The power converter is a three-phase full-bridge controllable rectifier, and the excitation regulation circuit is an asymmetrical H-bridge circuit.

[0032] In this embodiment, the electrically excited doubly salient pole motor is in high-speed power generation operation and is driven to rotate by an external drive device. After the controller sampling circuit collects the DC bus voltage and excitation current, the DSP performs dual closed-loop PID calculations for the outer loop of the bus voltage and the inner loop of the excitation current, and converts the calculation results into a switching duty cycle drive signal, which is output to the asymmetrical H-bridge to maintain the bus voltage at the reference value. The DSP simultaneously outputs a unified boost switching signal and a synchronous rectification enable signal to the FPGA. The unified boost signal is a logic signal with a fixed duty cycle, and the synchronous rectification enable signal is divided into high level and low level. The FPGA receives the unified boost signal, the synchronous rectification enable signal, and the three-phase current sampling feedback signal. The FPGA internally performs digital filtering, direction determination, and threshold determination on the three-phase current signal, and generates the final drive signal for each bridge arm based on the state of the unified boost switching signal and the synchronous rectification enable signal. When the unified boost switch signal is high, all three phase upper bridge arms are simultaneously turned on, while all three phase lower bridge arms are turned off. When the unified boost switch signal is low, if the synchronous rectification enable signal is high, the corresponding upper and lower bridge arm switches are turned on according to the synchronous rectification on / off judgment, achieving synchronous rectification. If the synchronous rectification enable signal is low, all bridge arm switches are turned off. Ultimately, equivalent synchronous boost control under high-speed conditions is achieved without relying on rotor position sensors.

[0033] like Figure 2 The diagram shows the principle of the three-phase full-bridge controllable rectifier power generation system in this invention being equivalent to a synchronous boost circuit. The upper part of the diagram shows the electrically excited doubly salient pole motor power generation system based on a three-phase full-bridge controllable rectifier, and the lower part shows the equivalent synchronous boost circuit structure. DSEG is the electrically excited doubly salient pole generator body. In the equivalent boost control method, its three-phase windings are equivalent to the input voltage V of the synchronous boost circuit. in and inductor L eq When the unified boost signal is high, the three upper bridge arm switches Q1, Q3, and Q5 of the three-phase full-bridge controllable rectifier are equivalent to the boost control switch Q7; when the unified boost signal is low and the synchronous rectification enable signal is high, all switches of the three-phase full-bridge controllable rectifier are turned on by the conduction judgment based on the current threshold, and are equivalent to the synchronous rectification control switch Q8.

[0034] like Figure 3 The diagram shown is a schematic of the conduction scheme of the equivalent synchronous boost control method of the present invention, wherein i a i b i cThese represent the three-phase currents A, B, and C, respectively. Q is the unified boost signal, and T1~T6 are the turn-on signals for the six switches of the three-phase full-bridge controllable rectifier. The conduction interval marked with a diagonal line is the boost conduction interval. Within this interval, Q is at a high level, forcibly turning on all upper bridge arm switches and forcibly turning off all lower bridge arm switches. The conduction interval marked with a solid color block is the synchronous rectification conduction interval. Within this interval, if the synchronous rectification enable signal is at a high level, the corresponding switch is turned on based on the current threshold judgment method to achieve synchronous rectification conduction control; if the synchronous rectification enable signal is at a low level, all switches are turned off.

[0035] like Figure 4 The diagram illustrates the switching transistor conduction judgment method based on current threshold during the synchronous rectification implementation of this invention, along with the judgment process. Taking phase A current as an example, when phase A current is negative and less than the reverse current threshold, the lower bridge arm switch of phase A remains on, and the upper bridge arm switch of phase A remains off; when phase A current positively crosses the reverse current threshold, both the upper and lower bridge arm switches of phase A are off; when phase A current positively crosses the positive current threshold, the upper bridge arm switch of phase A starts and remains on, and the lower bridge arm switch of phase A remains off; when phase A current reversely crosses the positive current threshold, both the upper and lower bridge arm switches of phase A are off; when phase A current reversely crosses the reverse current threshold, the system returns to the first state, with the lower bridge arm switch of phase A remaining on and the upper bridge arm switch of phase A remaining off. The synchronous rectification conduction judgment method's judgment process within each sampling period consists of the following steps:

[0036] 1) Phase current i of phase x x Perform sampling and filtering, x=a, b, c;

[0037] 2) Determine whether synchronous rectification is enabled based on the synchronous rectification enable signal;

[0038] 3) If not enabled, the current loop ends, conduction is not performed, and the process returns to step 1; if enabled, proceed to step 4.

[0039] 4) Determine i x Is it greater than the forward current threshold i? thpos If yes, proceed to step 5; otherwise, proceed to step 6.

[0040] 5) Set the synchronous rectification turn-on logic to turn on the upper bridge arm of phase x, and the current loop ends;

[0041] 6) Determine i x Is it less than the reverse current threshold i? thneg If yes, proceed to step 7; otherwise, end the current loop, do not activate, and return to step 1.

[0042] 7) Set the synchronous rectification turn-on logic to turn on the lower bridge arm of phase x, and the current loop ends.

[0043] like Figure 5 The figure shows the experimental results waveforms of the equivalent synchronous boost control method for electrically excited doubly salient pole motors proposed in this invention. Taking the A-phase current as an example, SIG in the figure... A_Up and SIG A_Up These are the on signals for connecting the upper and lower bridge arm switching transistors of phase A winding, respectively. a The waveform of phase A current, i f This is the excitation current. After applying the equivalent boost control method, the phase current amplitude is effectively increased, the MOSFET replaces the diode to achieve synchronous rectification, the power output capability of the power generation system is improved, and controller losses are suppressed.

[0044] like Figure 6 The diagram shows a comparison of controller losses between the proposed equivalent synchronous boost control method for electrically excited doubly salient pole motors and the traditional uncontrolled rectifier. The blue bars represent the conduction losses of the uncontrolled rectifier diode rectifier, while the red and green bars represent the sum of the conduction and switching losses of the three-phase full-bridge controlled rectifier at synchronous rectifier current thresholds of 5A and 20A, respectively. As the power level of the power generation system increases, the conduction losses of the diode rectifier increase rapidly. At a power generation capacity of 100kW, the conduction loss of the uncontrolled rectifier diode rectifier reaches 1066W. However, using the proposed equivalent synchronous boost control, at a power generation capacity of 100kW, the controller losses are suppressed to only 215W and 280W, respectively. Compared to the traditional control method, the reduction in controller losses reaches 79.8% and 73.7%, respectively.

[0045] like Figure 7 The diagram shows the efficiency distribution of the equivalent synchronous boost control method for an electrically excited doubly salient pole motor proposed in this invention. The method is applied under the following conditions: speed 16000 r / min, power generation 12 kW. Under the optimal control method, the power generation system efficiency reaches 90.2%, while the efficiency is 85% when only synchronous rectification control is applied. Under the same conditions, the efficiency of a traditional power generation system based on uncontrolled rectification is only 84.1%. The proposed method improves the overall efficiency of the power generation system by 6.1%.

[0046] This embodiment designs an equivalent synchronous boost control method for a high-speed electrically excited doubly salient pole motor generator system, belonging to the field of variable reluctance motor control technology. Specifically, the proposed equivalent synchronous boost control method for electrically excited doubly salient pole motors mainly includes a boost control implementation stage, a synchronous rectification conduction judgment stage, and a synchronous boost logic signal generation stage. Its control principle is as follows: the digital signal processing unit generates an excitation control signal and a unified boost control signal based on the DC bus voltage and excitation current; the field-programmable logic unit filters and determines the direction of the three-phase current; when the unified boost control signal is high, the three-phase upper bridge arm switches are simultaneously turned on to form an equivalent boost state; when the unified boost control signal is low, the corresponding bridge arm switches are turned on according to the current direction of each phase to achieve synchronous rectification. This method eliminates the need for rotor position sensors and additional voltage detection circuits, reducing controller losses and improving the output capability and efficiency of the electrically excited doubly salient pole motor generator system under high-speed operating conditions.

[0047] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An equivalent synchronous boost control method for an electrically excited doubly salient pole motor, characterized in that, This method is used in a power generation system including an electrically excited doubly salient pole motor, the method comprising: S1. Collect the actual three-phase current and excitation current of the electrically excited doubly salient pole motor; S2. PI regulation is performed based on the deviation between the excitation current reference value and the actual excitation current. S3. After filtering the actual three-phase current, determine the direction of the phase current; S4. When the unified boost switch signal is at a high level, the phase current amplitude is increased through boost control; S5. When the unified boost switch signal is at a low level, the corresponding bridge arm is assigned a synchronous rectification turn-on signal according to the determination result of the phase current direction. In the non-boost interval, the freewheeling path is undertaken by the MOSFET.

2. The method according to claim 1, characterized in that, The power generation system includes: the electrically excited doubly salient pole generator, a three-phase full-bridge controllable rectifier, an excitation power supply unit, a DC bus capacitor, a load, a sampling circuit, a digital signal processor (DSP), and a field-programmable gate array (FPGA).

3. The method according to claim 1, characterized in that, S3 includes: The current of each phase is compared with preset positive current conduction thresholds and negative current conduction thresholds. The comparison method for the current of a single phase includes: If the current is greater than the positive threshold, the current direction of this phase is determined to be positive; if it is less than the negative threshold, the current direction of this phase is determined to be negative.

4. The method according to claim 3, characterized in that, Also includes: If the current magnitude is between the positive and negative thresholds, the current of this phase is determined to be in the uncertain range near the zero crossing point, and synchronous rectification is not triggered.

5. The method according to claim 1, characterized in that, S4 include: When the unified boost switch signal is at a high level, it controls the three-phase upper bridge arm MOSFETs to turn on simultaneously, and all lower bridge arm switching devices to turn off. Increasing the phase current amplitude through boost control includes: , where i p-Boost For the phase current amplitude under boost control, i p-DR To control the phase current amplitude under uncontrolled rectification, i a Let e ​​be the phase A current. a , e b , e c The electromotive forces of the three-phase windings A, B, and C are respectively, r p u is the equivalent resistance of the phase winding. DC This is the bus voltage.

6. The method according to claim 1, characterized in that, In S5, the comparison methods for a single-phase current include: If the current direction of this phase is positive, then the corresponding upper bridge arm switching device will be turned on. If the current direction of this phase is negative, the corresponding lower bridge arm switching device is turned on.

7. The method according to claim 6, characterized in that, Also includes: When the current of this phase is in the uncertain region near the zero crossing point, both the upper and lower bridge arms of this phase remain off, and the current is either naturally freewheeled by the anti-parallel diode of this phase or waits for the next stable determination region.

8. The method according to claim 1, characterized in that, Also includes: Real-time recording of current waveforms and calculation of losses, including calculation models for MOSFET conduction losses, diode conduction losses, and MOSFET switching losses. P cond-MOS P cond-D and P switch-MOS V represents the conduction loss of the MOSFET and the diode, and the switching loss of the MOSFET. ON-MOS and V ON-D These are the forward voltage drops of the MOSFET and the diode, respectively, and are respectively quantized by the current i flowing through the MOSFET. x-MOS and the current i flowing through the diode x-D Decision, f s E is the switching frequency. ON and E OFF The energies for turning on and off the MOSFET are denoted as a, b, and c, which represent phases A, B, and C, respectively.

9. The method according to claim 1 or 2, characterized in that, Also includes: After the FPGA generates the synchronous boost turn-on signal and the synchronous rectification turn-on signal, it performs protection operations, including: shoot-through protection for the upper and lower transistors of the same bridge arm and overcurrent protection; The dead time includes: preventing shoot-through failures caused by overlapping drive switching of upper and lower switching devices on the same bridge arm; The overcurrent protection includes shutting off the corresponding drive signal when the phase current exceeds a set threshold.

Images