A direct voltage universal variable excitation switched reluctance generator converter and control method thereof

Abstract

A kind of direct voltage global variable excitation switched reluctance generator converter and its control method, converter is composed of six switching tubes, three-phase winding, five diodes, three inductors, four capacitors, variable excitation voltage is realized by fifth switching tube and sixth switching tube, there is only one ground terminal in converter, also no isolation transformer, the number of switching tubes is relatively less, voltage output can be directly lifted in work, and excitation voltage is introduced in power generation stage, i.e. by adjusting excitation voltage, direct influence can be exerted on the excitation and power generation global of each phase winding work;It is suitable for the application of various application occasions in the field of small and medium power high-speed switched reluctance generator system.

Description

Technical Field

[0001] This invention relates to the field of switched reluctance motors, specifically to a novel switched reluctance generator converter with direct voltage boost, global variable excitation, a small number of switching transistors, and no ground isolation, and its control method. Background Technology

[0002] Switched reluctance motors have a simple and robust structure, with no windings or permanent magnets on the rotor, and are easy to dissipate heat, making them particularly suitable for high-speed operation. Compared with various common AC and DC motors, switched reluctance motors show their advantages at high speeds.

[0003] Although there is not much research on switched reluctance generators and even less application, with the rapid development of DC microgrids, small wind power and distributed generation, the advantages of switched reluctance generators have gradually become apparent. This is because switched reluctance generators directly generate DC power, which can reduce the rectification stage.

[0004] In the operation of switched reluctance generator systems, the power converter, also known as the inverter, plays a more important role than other traditional motor inverters. Generally speaking, for example, the DC voltage directly generated by the classic asymmetrical half-bridge switched reluctance generator power converter is often relatively low. It needs to be boosted by a DC / DC boost stage before being connected to the grid or used by loads with higher voltage requirements. Therefore, from the perspective of new inverter design, the output voltage of the inverter can be directly boosted.

[0005] The number of switching transistors used in a switched reluctance generator converter is related to the amount of power loss during power conversion and the complexity of control. Therefore, a converter with fewer switching transistors generally has a higher cost-performance ratio while achieving the same function.

[0006] Variable excitation voltage switched reluctance generator control systems have become a hot topic in the domestic industry in recent years. By adjusting the excitation voltage, performance improvements such as MPPT control or other control methods can be achieved, and it can even replace current chopping and switching angle control. However, most variable excitation voltage methods apply influence during the excitation stage, and the generation stage can only be indirectly affected by the early excitation stage. In fact, the generation stage is the core of the power generation capacity of the entire switched reluctance generator system. If direct control can be applied directly during the generation stage, it will undoubtedly have great potential.

[0007] However, in addition to achieving functions such as variable excitation voltage, switched reluctance generator converters often introduce problems such as different ground terminals and the need for transformer isolation, which in turn increase size, weight, cost, losses, and reduce power generation efficiency. Summary of the Invention

[0008] Based on the above background technology, this invention proposes a novel converter and its control method for a switched reluctance generator that directly boosts the output voltage, has a small number of switching transistors, can directly introduce excitation voltage to exert direct influence during the power generation stage (i.e., can achieve variable excitation control across the entire range), has a simple structure without isolation links, and shares a common ground. It is suitable for applications in the field of small and medium power high-speed switched reluctance generator systems.

[0009] The technical solution of this invention is as follows:

[0010] A step-up, fully variable-excitation switched reluctance generator converter comprises a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first phase winding, a second phase winding, a third phase winding, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor, a third capacitor, and a fourth capacitor. The anode of the first switch is connected to the anodes of the second and third switches, one end of the second inductor, one end of the third inductor, and one end of the fourth capacitor. The cathode of the first switch is connected to one end of the first phase winding, the cathode of the second switch is connected to one end of the second phase winding, and the cathode of the third switch is connected to one end of the third phase winding. The other end of the first phase winding is connected to the other end of the second phase winding, and the other end of the third phase winding is connected to the other end of the third phase winding. One end of the first diode anode and the second diode anode are connected. The cathode of the first diode is connected to the anode of the fourth switch, the anode of the third diode, and one end of the first inductor. The cathode of the second diode is connected to the other end of the first inductor and one end of the first capacitor. The other end of the first capacitor is connected to the cathode of the third diode, one end of the second capacitor, and the anode of the fifth switch, and serves as the positive terminal of the switched reluctance generator output. The other end of the second capacitor is connected to the cathode of the fourth switch, the anode of the fourth diode, the anode of the fifth diode, and the other end of the fourth capacitor, and serves as the negative terminal of the switched reluctance generator output. The cathode of the fifth switch is connected to the anode of the sixth switch and one end of the third capacitor. The other end of the third capacitor is connected to the cathode of the fourth diode and the other end of the second inductor. The cathode of the sixth switch is connected to the cathode of the fifth diode and the other end of the third inductor.

[0011] This invention discloses a control method for a direct-drive, fully variable-excitation switched reluctance generator converter. Based on the working principle of the switched reluctance generator, according to its rotor position information, when the first phase winding needs to be engaged, the first and fourth switching transistors are first closed, entering the excitation stage of the first phase winding. The excitation power supply, i.e., the fourth capacitor side, supplies power to the first phase winding through the first and fourth switching transistors for excitation. Simultaneously, the first capacitor and the first inductor are charged. When the excitation stage needs to end according to the rotor position information, the fourth switching transistor is disconnected, entering the generation stage. The excitation power supply, the first phase winding, and the first inductor are connected in series and output electrical energy to the generation output terminal through the first switching transistor. At the same time, the excitation power supply, the first phase winding, and the first capacitor are also connected in series and output electrical energy to the generation output terminal through the first switching transistor. When the generation stage needs to end according to the rotor position information, the first switching transistor is disconnected, and the operation of the first phase winding ends.

[0012] Based on the rotor position information, when the second phase winding and the third phase winding need to be put into operation, the first switch tube can be replaced by the second switch tube and the third switch tube respectively. The working process is exactly the same as that of the first phase winding.

[0013] The excitation power supply, i.e., the excitation voltage, is regulated by controlling the fifth and sixth switching transistors. Both transistors operate in PWM mode with the same switching frequency. The duty cycle of the fifth transistor remains constant at 0.5, while the duty cycle of the sixth transistor is greater than 0.5 and adjustable. Furthermore, the turn-on timing of the sixth transistor lags behind that of the fifth transistor, with a phase difference of [missing information]. D is the duty cycle of the sixth switch.

[0014] The main technical effects of this invention are:

[0015] During the operation of each phase winding, the generated voltage at the output terminal is significantly greater than the excitation voltage at the input terminal, achieving the effect of direct voltage boost. This can directly meet the requirements of loads with higher voltage requirements or the higher voltage demands of DC microgrids.

[0016] Adjusting the excitation voltage requires two switching transistors (the fifth and sixth switching transistors). Apart from these, the number of switching transistors required for the operation of a switched reluctance generator is N+1, where N is the number of phase windings. It can be seen that, in the industry, this is a switched reluctance generator converter with a relatively small number of switching transistors.

[0017] The converter of this invention can adjust the excitation voltage, which meets the needs of performance improvement of variable excitation switched reluctance generator system. More importantly, the excitation voltage not only plays a role in the excitation stage, but also in the generation stage. That is, the phase winding can be directly controlled in the generation stage by adjusting the excitation voltage, such as the phase winding current and the generation voltage, which greatly improves the system control performance.

[0018] Based on the above functions, there is no isolation transformer in the entire converter and only one ground terminal. Although it is not suitable for high power applications, it greatly reduces the size, weight, cost, and losses of the converter. Attached Figure Description

[0019] Figure 1 The diagram shown is a circuit structure diagram of a direct-drive global variable excitation switched reluctance generator converter according to the present invention. Detailed Implementation

[0020] This embodiment describes a direct-drive, fully variable-excitation switched reluctance generator converter, the circuit structure of which is shown in the attached figure. Figure 1 As shown, the switched reluctance generator is a three-phase 6 / 4-pole structure. The converter consists of a first switch V1, a second switch V2, a third switch V3, a fourth switch V4, a fifth switch V5, a sixth switch V6, a first phase winding M, a second phase winding N, a third phase winding P, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a first inductor L1, a second inductor L2, a third inductor L3, a first capacitor C1, a second capacitor C2, and a sixth capacitor V6. The circuit consists of three capacitors C3 and a fourth capacitor C4. The anode of the first switching transistor V1 is connected to the anodes of the second switching transistor V2 and the third switching transistor V3, one end of the second inductor L2, one end of the third inductor L3, and one end of the fourth capacitor C4. The cathode of the first switching transistor V1 is connected to one end of the first phase winding M. The cathode of the second switching transistor V2 is connected to one end of the second phase winding N. The cathode of the third switching transistor V3 is connected to one end of the third phase winding P. The other end of the first phase winding M is connected to the other end of the second phase winding N and the other end of the third phase winding P. The first diode D1 has an anode, and the second diode D2 has an anode. The cathode of the first diode D1 is connected to the anode of the fourth switch V4, the anode of the third diode D3, and one end of the first inductor L1. The cathode of the second diode D2 is connected to the other end of the first inductor L1 and one end of the first capacitor C1. The other end of the first capacitor C1 is connected to the cathode of the third diode D3, one end of the second capacitor C2, and the anode of the fifth switch V5, serving as the positive terminal for the switched reluctance generator output. The other end of the second capacitor C2 is connected to the cathode of the fourth switch V4, the anode of the fourth diode D4, the anode of the fifth diode D5, and the other end of the fourth capacitor C4, serving as the negative terminal for the switched reluctance generator output, and also as the negative terminal for the input and output of the variable excitation circuit. The cathode of the fifth switch V5 is connected to the anode of the sixth switch V6 and one end of the third capacitor C3. The other end of the third capacitor C3 is connected to the cathode of the fourth diode D4 and the other end of the second inductor L2. The cathode of the sixth switch V6 is connected to the cathode of the fifth diode D5 and the other end of the third inductor L3.

[0021] The circuit consisting of the fifth switch V5, the sixth switch V6, the fourth diode D4, the fifth diode D5, the second inductor L2, the third inductor L3, the third capacitor C3, and the fourth capacitor C4 is a variable excitation circuit. Its input terminal comes from the output terminal of the switched reluctance generator, and its output terminal, namely the terminal of the fourth capacitor C4, serves as the excitation power supply when each phase winding is working. The voltage across the fourth capacitor C4 is the excitation voltage, and the input voltage, namely the voltage at the output terminal of the switched reluctance generator, is the generating voltage.

[0022] All switching transistors are high-frequency, three-terminal, fully controlled power electronic switching devices, such as MOSFETs, IGBTs, and other silicon carbide or gallium nitride devices.

[0023] This embodiment describes a control method for a direct-drive, fully variable-excitation switched reluctance generator converter. Based on the working principle of the switched reluctance generator and its rotor position information, when the first phase winding M needs to be engaged, the first switch V1 and the fourth switch V4 are first closed, entering the excitation stage of the first phase winding M. The excitation power supply, i.e., the fourth capacitor C4 side, supplies power to the first phase winding M for excitation through the first switch V1 and the fourth switch V4, i.e.: C4-V1-M-D1-V4-C4. Simultaneously, a loop exists: C2-C1-L1-V4-C2, meaning that the first capacitor C1 and the first inductor L1 are charged. When the excitation stage needs to end according to the rotor position information, the fourth switch V4 is disconnected, entering the generator phase. During the power generation phase, the excitation power supply, the first phase winding M, and the first inductor L1 are connected in series and output electrical energy to the power generation output terminal via the first switch V1, i.e.: C4-V1-M-D2-L1-D3-C2 (power generation output terminal)-C4. Simultaneously, the excitation power supply, the first phase winding M, and the first capacitor C1 are connected in series and output electrical energy to the power generation output terminal via the first switch V1, i.e.: C4-V1-M-D2-C1-C2-C4. It is evident that in the two power generation output circuits during the power generation phase, the excitation voltage is significantly lower than the generation voltage, effectively boosting the voltage output. Furthermore, the excitation voltage directly participates in the power generation output during the power generation phase; therefore, changing the excitation voltage can regulate the operating performance. Based on the rotor position information, when the power generation phase needs to end, the first switch V1 is disconnected, and the first phase winding M ceases operation.

[0024] Based on the rotor position information, when the second phase winding N and the third phase winding P need to be put into operation, the first switch V1 can be replaced by the second switch V2 and the third switch V3 respectively. The working process is the same as that of the first phase winding M.

[0025] To improve the operating performance of the switched reluctance generator, the excitation voltage needs to be adjusted. This adjustment is achieved through the fifth switch V5 and the sixth switch V6. Both switches V5 and V6 operate in PWM mode, with the same switching frequency, operating at high frequencies above 10kHz. The duty cycle of switch V5 remains constant at 0.5, while the duty cycle of switch V6 is greater than 0.5 and adjustable. Furthermore, the turn-on time of switch V6 lags behind that of switch V5, with a phase difference of [missing information]. D is the duty cycle of the sixth switch V6. The purpose is to ensure that the two simultaneously turned-on states have equal durations in the four mutual switching states of the two switches. Thus, the duty cycle of the sixth switch V6 is adjusted based on a value greater than 0.5 to regulate the output excitation voltage and meet the needs of different control performance.

[0026] Specifically, for the excitation voltage regulation of the variable excitation circuit, when the fifth switch V5 and the sixth switch V6 are both on, the input terminal (generating voltage terminal) receives current through the fifth switch V5, which flows through the V6-L3 and C3-L2 branches respectively, and outputs to the output terminal (fourth capacitor C4) while simultaneously charging the third capacitor C3, the second inductor L2, and the third inductor L3. When the fifth switch V5 is on and the sixth switch V6 is off, in addition to the output from the V5-C3-L2-C4 circuit, the third inductor L3... The fifth diode D5 discharges and outputs; when the fifth switch V5 is off and the sixth switch V6 is on, the second inductor L2 discharges and outputs through the fourth diode D4, and the third capacitor C3 discharges and outputs together with the third inductor L3 through the sixth switch V6; according to the above working process, it is very convenient to obtain that the output voltage of the variable excitation circuit, i.e., the excitation voltage, is equal to D / 2 times the input terminal generation voltage. That is, the variable excitation circuit is a step-down adjustable circuit, which matches the main circuit directly boosting the voltage output relative to the input side excitation voltage when each phase winding is working to generate the generation voltage.

Claims

1. A direct-drive, fully variable-excitation switched reluctance generator converter, comprising a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first phase winding, a second phase winding, a third phase winding, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor, a third capacitor, and a fourth capacitor, characterized in that the anode of the first switch is connected to the anode of the second switch, the anode of the third switch, one end of the second inductor, one end of the third inductor, and one end of the fourth capacitor; the cathode of the first switch is connected to one end of the first phase winding; the cathode of the second switch is connected to one end of the second phase winding; the cathode of the third switch is connected to one end of the third phase winding; and the other end of the first phase winding is connected to the other end of the second phase winding and the third phase winding. The first diode anode and the second diode anode are connected to the other end of the circuit. The first diode cathode is connected to the fourth switch anode, the third diode anode, and one end of the first inductor. The second diode cathode is connected to the other end of the first inductor and one end of the first capacitor. The other end of the first capacitor is connected to the third diode cathode, one end of the second capacitor, and the fifth switch anode, and serves as the positive terminal of the switched reluctance generator output. The other end of the second capacitor is connected to the fourth switch cathode, the fourth diode anode, the fifth diode anode, and the other end of the fourth capacitor, and serves as the negative terminal of the switched reluctance generator output. The fifth switch cathode is connected to the sixth switch anode and one end of the third capacitor. The other end of the third capacitor is connected to the fourth diode cathode and the other end of the second inductor. The sixth switch cathode is connected to the fifth diode cathode and the other end of the third inductor.

2. The control method for a direct-drive, fully variable-excitation switched reluctance generator converter according to claim 1, characterized in that: Based on the working principle of the switched reluctance generator, according to its rotor position information, when the first phase winding needs to be put into operation, the first and fourth switching transistors are closed first, entering the excitation stage of the first phase winding. The excitation power supply, i.e., the fourth capacitor side, supplies power to the first phase winding through the first and fourth switching transistors for excitation. At the same time, the first capacitor and the first inductor are charged. According to the rotor position information, when the excitation stage needs to end, the fourth switching transistor is opened, entering the generation stage. The excitation power supply, the first phase winding, and the first inductor are connected in series and output electrical energy to the generation output terminal through the first switching transistor. At the same time, the excitation power supply, the first phase winding, and the first capacitor are connected in series and also output electrical energy to the generation output terminal through the first switching transistor. Based on the rotor position information, when the power generation phase needs to end, the first switch tube is disconnected, and the first phase winding ends its operation. Based on the rotor position information, when the second phase winding and the third phase winding need to be put into operation, only the second switch and the third switch need to be replaced by the first switch respectively, and the working process is exactly the same as that of the first phase winding. The excitation power supply, i.e., the excitation voltage, is regulated by controlling the fifth and sixth switching transistors. Both transistors operate in PWM mode with the same switching frequency. The duty cycle of the fifth transistor remains constant at 0.5, while the duty cycle of the sixth transistor is greater than 0.5 and adjustable. Furthermore, the turn-on timing of the sixth transistor lags behind that of the fifth transistor, with a phase difference of [missing information]. D is the duty cycle of the sixth switch.

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