An electric excitation control system and control method for a generator

Abstract

The present invention discloses an electrically excited control system for a generator. The generator uses residual magnetism or an excitation voltage to generate a three-phase sinusoidal voltage; a three-phase rectifier and filter circuit converts the three-phase sinusoidal voltage into a DC bus voltage; a DC / DC circuit performs voltage conversion on the DC bus voltage; when the DC voltage after conversion by the DC / DC circuit reaches the rated value of the relay coil voltage, the relay contact opens; the excitation control circuit generates an excitation voltage, and when the relay contact opens, the excitation voltage is output to the excitation winding. The present invention also discloses a control method for an electrically excited generator, which is a method of self-excitation conversion to other-excitation. When the generator starts excitation, the terminal voltage is generated through the residual magnetism of the motor, and then the terminal voltage is used to supply power to the excitation control system, and the power generation stability is controlled through the excitation control system. The present invention effectively solves the situation that the traditional other-excitation method requires an independent external power supply and cannot ensure stable power generation when conditions such as the motor temperature and load change, and improves the environmental adaptability and anti-interference ability of the generator.

Description

Technical Field

[0001] The invention belongs to the technical field of generators, and particularly relates to an electric excitation control system for a generator. Background Art

[0002] Electric excitation power generation is a technology that controls the magnetic field strength by controlling the magnitude of the excitation current, thereby controlling the terminal voltage of the generator. Currently, the commonly used excitation methods for electric excitation generators include: separately excited mode, self-excited mode, series excitation, compound excitation, etc. The separately excited mode is a method of providing an excitation current for the motor using an excitation circuit, but it requires a power supply or a battery, and is not suitable for miniaturized generator sets or occasions where the generator needs to work independently. The self-excited mode uses the residual magnetism inside the generator to induce an electromotive force in the armature winding. Under the action of this electromotive force, an excitation current is generated in the excitation circuit. The generation of the excitation current will strengthen the magnetic field in the motor, further increase the electromotive force induced in the armature winding, and further increase the excitation current. In this way, they promote each other until the terminal voltage and the excitation current of the motor reach equilibrium. However, as the generator operates, the temperature rise of the motor will affect the resistance value of the excitation winding, and further affect the voltage value at the generator terminal. In addition, when the generator is loaded, the voltage drop of the load current on the internal resistance of the motor will also cause the terminal voltage to drop. The drop in the terminal voltage will cause the excitation current to be smaller and lead to a further drop in the terminal voltage. To overcome this shortcoming, a series excitation winding is added to the motor. The series excitation winding is connected in series with the load circuit. As the load increases, the magnetic potential of the series excitation winding increases, causing the induced electromotive force of the motor to increase correspondingly, so that the terminal voltage can be basically kept balanced. However, this method still does not have good regulation performance when dealing with load changes, temperature changes, and generator speed changes, and it is easy to cause the quality of the electric energy output by the generator to decline, resulting in the load not working or even damaging the load. Summary of the Invention

[0003] The object of the present invention is to overcome the above-mentioned defects and provide an electric excitation control system for a generator and its control method. The electric excitation control system for a generator includes a generator, a three-phase rectifier filter circuit, a DC / DC circuit, a relay, and an excitation control loop; the generator generates a three-phase sinusoidal voltage by using residual magnetism or an excitation voltage; the three-phase rectifier filter circuit converts the three-phase sinusoidal voltage into a DC bus voltage; the DC / DC circuit performs voltage conversion on the DC bus voltage to obtain a converted DC voltage, preferably a 24V output voltage; the relay contact is in a normally closed state, and when the DC / DC circuit outputs the converted DC voltage, the relay contact disconnects, realizing the switching between the self-excitation mode and the he-excitation mode; the excitation control loop controls the excitation voltage according to the value of the DC bus voltage, and when the relay circuit is disconnected, the excitation control loop outputs the excitation voltage to both ends of the excitation winding. The electric excitation control method of the present invention is a self-excitation to he-excitation method. When the generator is starting up, it uses the residual magnetism of the motor to generate the terminal voltage. After the motor stably outputs, it uses the excitation control loop to control the stability of the output voltage. The present invention effectively solves the situation that the traditional he-excitation method requires an independent external power supply and the traditional self-excitation method cannot ensure stable power generation when conditions such as motor temperature, load, and input speed change, improving the environmental adaptability and anti-interference ability of the generator.

[0004] To achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0005] An electric excitation control system for a generator, including a generator, a three-phase rectifier filter circuit, a DC / DC circuit, a relay, and an excitation control loop;

[0006] The generator includes an excitation winding; the generator generates a three-phase sinusoidal voltage by using residual magnetism, or receives an excitation voltage input to both ends of the excitation winding by the excitation control loop to generate a three-phase sinusoidal voltage, and outputs the three-phase sinusoidal voltage to the three-phase rectifier filter circuit;

[0007] The three-phase rectifier filter circuit receives the three-phase sinusoidal voltage input by the generator, converts the three-phase sinusoidal voltage into a DC bus voltage, and outputs the DC bus voltage to the DC / DC circuit and the excitation control loop;

[0008] The DC / DC circuit receives the DC bus voltage input by the three-phase rectifier filter circuit. When the value of the DC bus voltage is less than the minimum input value of the DC / DC circuit, the DC / DC circuit does not work. When the value of the DC bus voltage is greater than or equal to the minimum input value of the DC / DC circuit, the DC / DC circuit performs DC conversion on the DC bus voltage to obtain a converted DC voltage, and outputs the converted DC voltage to the relay and the excitation control loop;

[0009] The positive and negative output terminals of the relay are connected to both ends of the exciting winding, and the relay contacts are in the normally closed state; after the relay receives the converted DC voltage input by the DC / DC circuit, the relay contacts are disconnected to realize the switching between the self-excitation mode and the separate-excitation mode; the converted DC voltage is equal to the rated value of the relay coil.

[0010] The exciting control circuit is powered by the converted DC voltage input by the DC / DC circuit; the exciting control circuit receives the DC bus voltage input by the three-phase rectifier filter circuit and generates an exciting voltage controlled by the value of the DC bus voltage. After the relay contacts are disconnected, the exciting control circuit outputs the exciting voltage to both ends of the exciting winding.

[0011] Further, the DC / DC circuit is a 90 - 350V wide-range input and 24V output DC / DC conversion circuit.

[0012] The rated value of the relay coil is 24V.

[0013] Both ends of the relay coil are connected to the output terminal of the DC / DC circuit, and the relay contacts are disconnected after the DC / DC circuit outputs a 24V DC voltage.

[0014] Further, the exciting control circuit includes a voltage sampling circuit, a PWM control circuit, a signal driving circuit, and an exciting output circuit.

[0015] The voltage sampling circuit receives the DC bus voltage input by the three-phase rectifier filter circuit, performs proportional sampling on the DC bus voltage to obtain the DC bus voltage sampling value, and outputs the DC bus voltage sampling value to the PWM control circuit.

[0016] The PWM control circuit generates a PWM exciting control signal according to the DC bus voltage sampling value and outputs the PWM exciting control signal to the signal driving circuit.

[0017] The signal driving circuit amplifies the PWM exciting control signal and outputs it to the exciting output circuit.

[0018] The exciting output circuit generates an exciting voltage according to the amplified PWM exciting control signal, and the magnitude of the exciting voltage is related to the duty cycle of the PWM exciting control signal.

[0019] Further, the voltage sampling circuit uses the method of resistor voltage division to sample the DC bus voltage at a ratio of 1 / 140 to obtain the DC bus voltage sampling value.

[0020] Further, the PWM control circuit includes a pulse width modulation chip SG1524 and peripheral circuits.

[0021] The pulse width modulation chip SG1524 internally integrates an error amplifier, a sawtooth wave generator, a signal comparator, and a reference voltage source;

[0022] The peripheral circuit includes voltage dividing resistors, a sawtooth wave frequency setting resistor, and a capacitor;

[0023] The reference voltage source is divided by the voltage dividing resistor to obtain the reference voltage of the error amplifier;

[0024] The positive input terminal and the negative input terminal of the error amplifier respectively input the reference voltage of the error amplifier and the sampled value of the DC bus voltage. The error amplifier amplifies the error value between the reference voltage and the sampled value of the DC bus voltage to obtain a control signal, and outputs the control signal to the signal comparator;

[0025] The sawtooth wave generator uses the sawtooth wave frequency setting resistor and the capacitor to generate a sawtooth wave with a desired frequency, and outputs the sawtooth wave to the signal comparator;

[0026] The signal comparator compares the control signal with the sawtooth wave to obtain a PWM excitation control signal.

[0027] Further, the signal driving circuit includes a half-bridge driver IR2110;

[0028] The high-end input signal HIN of the half-bridge driver IR2110 is the PWM excitation control signal output by the PWM control circuit, and the low-end input signal LIN is a stable high level.

[0029] Further, the excitation output circuit is a half-bridge circuit, including two IGBTs, which are respectively the upper half-bridge tube and the lower half-bridge tube;

[0030] The amplified PWM excitation control signal output by the signal driving circuit controls the on and off of the upper half-bridge tube, and the lower half-bridge tube is in a constant conduction mode.

[0031] Further, the value of the excitation voltage is the product of the DC bus voltage and the duty cycle of the PWM excitation control signal;

[0032] When the DC bus voltage increases, the duty cycle of the PWM excitation control signal decreases, and the excitation voltage decreases; when the DC bus voltage decreases, the duty cycle of the PWM excitation control signal increases, and the excitation voltage increases.

[0033] Further, the three-phase rectifier filter circuit includes a three-phase uncontrolled bridge rectifier circuit and a capacitor filter circuit;

[0034] The three-phase uncontrolled bridge rectifier circuit rectifies the three-phase sinusoidal voltage into direct current, and then filters the direct current through the capacitor filter circuit to obtain a stable DC bus voltage.

[0035] A method for electrically exciting control of a generator, implemented by using the above-mentioned electrically exciting control system for a generator, includes:

[0036] In the self-excitation mode, the generator uses residual magnetism to generate continuously increasing three-phase sinusoidal voltages. After passing through a three-phase rectification and filtering circuit, the three-phase sinusoidal voltages generate a DC bus voltage. When the value of the DC bus voltage is less than the minimum input value of the DC / DC circuit, the DC / DC circuit does not work, and the relay circuit is in a closed state;

[0037] When the input value of the DC / DC circuit reaches the minimum input value, the DC / DC circuit works normally, outputs the converted DC voltage to the relay, the relay contact disconnects, and the generator switches from the self-excitation mode to the separate-excitation mode;

[0038] In the separate-excitation mode, the DC / DC circuit supplies power to the excitation control loop. The excitation control loop outputs an excitation voltage to both ends of the excitation winding. The excitation voltage generates a magnetizing current in the excitation winding, and the generator uses the magnetizing current to adjust the three-phase sinusoidal voltages.

[0039] The present invention has the following beneficial effects compared with the prior art:

[0040] (1) The present invention proposes an electrically exciting control system for a generator, innovatively adopting an excitation control method of self-excitation and separate-excitation conversion, effectively solving the problems that the traditional separate-excitation method requires an independent external power supply and the traditional self-excitation method cannot ensure stable power generation when conditions such as motor temperature, load, and input speed change. It effectively improves the environmental adaptability and anti-interference ability of the generator and reduces the equipment volume;

[0041] (2) The present invention uses a relay to achieve the conversion between the self-excitation and separate-excitation modes, and ingeniously achieves high reliability with a simple circuit;

[0042] (3) The excitation control circuit of the present invention uses a pure analog circuit to achieve closed-loop control of the excitation voltage, with fast response speed, simple implementation method, and high reliability;

[0043] (4) The excitation control scheme of the present invention uses a pure hardware closed-loop control circuit, which can quickly suppress the bus voltage fluctuation and improve the power output quality of the generator. Description of the Drawings

[0044] Figure 1 It is a structural block diagram of the electrically exciting control system for a generator in a preferred embodiment of the present invention;

[0045] Figure 2 It is a circuit diagram of the PWM control circuit in a preferred embodiment of the present invention;

[0046] Figure 3Circuit diagram of the signal drive circuit in a preferred embodiment of the present invention;

[0047] Figure 4 Circuit diagram of the excitation output circuit in a preferred embodiment of the present invention. Specific embodiments

[0048] The present invention will be described in detail below, and the features and advantages of the present invention will become clearer and more definite with these descriptions.

[0049] The special term "exemplary" here means "serving as an example, embodiment or illustration". Any embodiment described as "exemplary" here does not have to be construed as superior or better than other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings do not have to be drawn to scale unless otherwise specified.

[0050] The present invention provides an excitation system and control method combining self-excitation and separate excitation, which can realize excitation without an external power supply, and adjust the stability of the generator output voltage through the excitation control circuit after excitation, and can ensure that the generator outputs a stable voltage under the conditions of environmental temperature, load and speed changes.

[0051] Specifically, an electric excitation control system for a generator includes a generator, a three-phase rectifier filter circuit, a DC / DC circuit, a relay and an excitation control loop.

[0052] The generator includes a stator, a rotor and an excitation winding. The prime mover drives the rotor to rotate, and the motor uses residual magnetism or excitation current to generate a magnetic field. When the rotor rotates, a relative cutting magnetic force line movement is formed for the stator, and an induced electromotive force will be generated on the stator, and the motor can output a three-phase sinusoidal voltage.

[0053] The input of the three-phase rectifier filter circuit is the line voltage of the three-phase stator windings of the motor, and the three-phase rectifier filter circuit is used for rectifying and filtering the three-phase sinusoidal voltage to obtain a DC bus voltage.

[0054] The DC / DC circuit is used to convert the DC bus voltage, supply power to the excitation control loop and control the relay circuit.

[0055] The relay coil is connected to the output end of the DC / DC circuit, and the relay contacts are used for switching between the self-excitation and separate excitation modes of the motor.

[0056] The excitation control loop includes a voltage sampling circuit, a PWM control circuit, a signal drive circuit, and an excitation output circuit;

[0057] Preferably, the input of the voltage sampling circuit is the output voltage of the three-phase rectifier filter circuit. The voltage sampling circuit uses the resistor voltage division method to sample the DC bus voltage proportionally. The sampled DC bus voltage value is input to the PWM control circuit.

[0058] Preferably, the PWM control circuit uses an error amplifier to control the DC bus voltage sampling value to be close to the expected value of the motor output voltage, and outputs a PWM excitation control signal to control the excitation voltage.

[0059] Preferably, the signal drive circuit amplifies the PWM excitation control signal and outputs it to the excitation output circuit.

[0060] Preferably, the excitation output circuit uses two IGBTs to form a half-bridge circuit. The on / off of the upper-bridge IGBT is controlled by the PWM excitation control signal, and the lower-bridge IGBT is in a constant-on state. The excitation output circuit loads the excitation voltage across the two ends of the excitation winding. The value of the excitation voltage is the DC bus voltage multiplied by the duty cycle. Therefore, the value of the excitation current can be adjusted by using the duty cycle of the PWM excitation control signal, and further the value of the generator terminal voltage can be adjusted.

[0061] Preferably, the three-phase rectifier filter circuit uses three-phase uncontrolled bridge rectification to rectify the three-phase alternating current output by the motor into direct current, and then filters the direct current through a capacitor filter circuit to obtain a stable DC bus voltage.

[0062] Preferably, the relay circuit is used to control the on / off of the motor excitation winding. The positive and negative output terminals of the relay are connected to the positive and negative ends of the excitation winding. The relay is a normally closed relay, which is equivalent to the short circuit of the positive and negative ends of the excitation winding when the motor is not generating electricity. When the motor starts to excite, that is, at the beginning of operation, the positive and negative ends of the excitation winding are short-circuited through the relay, and the motor generates electricity through residual magnetism, which is a self-excitation method. After the generated voltage passes through the three-phase rectifier filter circuit and the DC / DC circuit transformation, and the DC / DC circuit can output a stable 24V voltage, the relay contact disconnects, and the excitation winding is no longer in a short-circuited state. The positive and negative of the excitation winding are respectively connected to the positive and negative ends of the excitation output of the excitation control circuit, and then the excitation voltage is output through the excitation control circuit to control the excitation current.

[0063] Preferably, the PWM control circuit consists of the chip SG1524 and its peripheral circuits. The SG1524 integrates an error amplifier, a sawtooth wave generator, a signal comparator, a reference voltage source, etc. internally. By externally connecting voltage-dividing resistors, the reference voltage of the error amplifier can be obtained by dividing the internal reference voltage source of the SG1524. The sampled value of the DC bus voltage obtained by the voltage sampling circuit is the actual voltage. The actual voltage and the reference voltage are simultaneously input into the error amplifier, and the parameters of the compensation link are set by externally connecting resistors, capacitors and other devices, then the control signal can be obtained inside the chip. The control signal is compared with the sawtooth wave generated by the sawtooth wave generator inside the chip to obtain the PWM excitation control signal, which is output to the signal drive circuit. The reference voltage is equal to the sampled value of the desired output voltage of the motor.

[0064] Preferably, the signal drive circuit includes a half-bridge driver IR2110 and its peripheral circuits. The high-end input is the PWM control signal, and the low-end input signal is a stable high level. The purpose is to increase the driving ability of the PWM control signal.

[0065] Preferably, the excitation output circuit mainly consists of an IGBT half-bridge. The amplified PWM excitation control signal output by the signal drive circuit controls the on-off of the upper tube of the IGBT half-bridge. The duty cycle of the PWM excitation control signal determines the effective value of the excitation voltage. After the excitation voltage is input into the excitation winding, an excitation current is generated to control the output voltage value of the generator to remain stable.

[0066] A method for controlling the electrical excitation of a generator includes:

[0067] 1) Using the prime mover to drive the generator rotor to rotate, using a normally closed relay to short-circuit the positive and negative ends of the excitation winding, using the residual magnetism in the generator to generate an excitation current, and outputting the terminal voltage, that is, three-phase sinusoidal voltage;

[0068] 2) Rectifying the terminal voltage of the motor through a three-phase rectifier filter voltage, and then converting the DC bus voltage into direct current through a DC / DC circuit to supply power to the control circuit;

[0069] 3) After the direct current output by the DC / DC circuit realizes a normal output of 24V, controlling the action of the relay contact to disconnect the short-circuited excitation winding;

[0070] 4) Sampling the DC bus voltage value after rectifying the output voltage of the generator, and using the PWM control circuit to generate a PWM excitation control signal;

[0071] 5) Amplifying the PWM excitation control signal through the signal drive circuit and inputting it into the excitation output circuit;

[0072] 6) The excitation output circuit adjusts the excitation voltage value across the excitation winding through the on-off of the IGBT to generate an excitation current and adjust the output voltage of the generator.

[0073] Example 1:

[0074] This embodiment will further elaborate on the content of the present invention in conjunction with the attached Figures 1 to 4 drawings.

[0075] As Figure 1 shown, an electric excitation control system for a generator includes a generator, a three-phase rectifier filter circuit, a DC / DC circuit, a relay circuit, and an excitation control loop.

[0076] The generator includes a stator, a rotor, a stator winding, and an excitation winding. When the generator operates, the prime mover drives the rotor of the generator to rotate. During self-excitation starting, the residual magnetic field in the motor is utilized. When the rotor rotates, a relative cutting magnetic field line movement is formed with respect to the stator, and an induced electromotive force is formed on the stator winding. Under the action of this electromotive force, an excitation current is generated in the excitation winding. The generation of the excitation current strengthens the magnetic field in the motor, further increases the induced electromotive force in the excitation winding, and further increases the excitation current. In this way, they promote each other, causing the output voltage of the generator to increase.

[0077] The function of the three-phase rectifier filter circuit is to rectify the three-phase alternating current output by the stator winding of the motor into direct current, and finally output a stable DC bus voltage through the filter circuit.

[0078] The function of the DC / DC circuit is to convert the DC bus voltage output by the three-phase rectifier filter circuit into 24V direct current to supply power to the excitation control loop and control the on / off of the relay.

[0079] The input of the relay circuit is the output voltage of the DC / DC circuit. The positive and negative terminals of the relay output are connected to the positive and negative terminals of the excitation winding. Preferably, the relay is a 24V normally closed relay. When the output voltage of the DC / DC circuit is less than 24V (i.e., the DC / DC circuit does not work and outputs 0V), the relay is in a closed state, and the positive and negative terminals of the generator excitation winding are short-circuited, and the generator is in a self-excitation state. When the output voltage of the DC / DC circuit reaches 24V (i.e., the DC / DC circuit is in a working state), the relay output contact disconnects, and the positive and negative of the excitation winding are respectively connected to the positive and negative excitation signal output terminals of the excitation control loop, and then the magnitude of the excitation current is controlled by the excitation control loop.

[0080] The excitation control loop includes a voltage sampling circuit, a PWM control circuit, a signal drive circuit, and an excitation output circuit.

[0081] Preferably, the voltage sampling circuit uses the method of resistor voltage division to sample the DC bus voltage at a ratio of 1 / 140 and input it into the PWM control circuit. The expected value of the DC bus voltage is 350V, and the sampled value is approximately 2.5V.

[0082] Preferably, the PWM control circuit includes a pulse width modulation chip SG1524 and its peripheral circuits, as Figure 2 shown. The SG1524 internally integrates an error amplifier, a sawtooth wave generator, a signal comparator, a reference voltage source, etc. By externally connecting voltage dividing resistors R7 and R8, the reference voltage of the reference voltage source inside the SG1524 can be divided to obtain the reference voltage of the error amplifier, which is input to the positive input terminal of the error amplifier. The negative input terminal of the error amplifier is the sampled value of the DC bus voltage. By externally connecting devices such as resistors and capacitors to the 9th pin of the SG1524, the parameters of the error amplifier compensation link can be set. After the SG1524 is powered on and works, a control signal can be obtained inside the chip. By configuring the values of R3 and C1 connected to the 6th and 7th pins of the chip, a sawtooth wave with a desired frequency can be obtained inside the chip. The control signal and the sawtooth wave are compared in the signal comparator to obtain a PWM excitation control signal (i.e., the Figure 2 , 3 PWM control signal in

[0083] ), which is output to the signal drive circuit. Figure 3 Preferably, as Figure 3 , the signal drive circuit includes a half-bridge driver IR2110 and its peripheral circuits. The high-end input signal HIN is the PWM control signal output by the SG1524, and the low-end input signal LIN is a stable high level. The input signal is amplified to enhance the driving ability of the signal, and the output signal is used to drive the IGBT of the excitation output circuit.

[0084] Preferably, as Figure 4 shown, the excitation output circuit consists of two IGBTs in a half-bridge form. The amplified PWM excitation control signal output by the signal drive circuit controls the on and off of the upper tube of the IGBT half-bridge. The lower tube of the IGBT is in a constant-on mode. The effective value of the excitation voltage is the PWM duty cycle multiplied by the DC bus voltage. After the excitation voltage is input to the excitation winding, an excitation current is generated. When the DC bus voltage is high, the duty cycle of the PWM excitation control signal decreases, the excitation current decreases, and the generator voltage decreases. Conversely, when the DC bus voltage is low, the duty cycle of the PWM excitation control signal increases, the excitation current increases, and the generator voltage increases. Therefore, the generator voltage can be controlled at the desired value.

[0085] Through experiments, the generator can generate electricity without an external power supply, and a stable terminal voltage can be obtained under the conditions of changes in ambient temperature, load, and speed.

[0086] An electric excitation control method for a generator includes:

[0087] 1) Using a prime mover to drive the generator rotor to rotate, using a normally closed relay to short-circuit the positive and negative terminals of the excitation winding, using the residual magnetism in the generator to generate an excitation current, and outputting an induced voltage, i.e., three-phase sinusoidal voltage, on the stator winding.

[0088] 2) Rectify the three-phase sinusoidal voltage through three-phase rectification and filtering to obtain the DC bus voltage, and then perform DC conversion on the DC bus voltage through DC / DC to supply power to the excitation control circuit and control the on / off of the relay circuit.

[0089] 3) After the DC / DC circuit normally outputs 24V, disconnect the short-circuited excitation winding by controlling the relay circuit;

[0090] 4) The voltage sampling circuit samples the DC bus voltage and inputs the sampled value into the chip SG1524 in the PWM control circuit to generate a PWM excitation control signal using SG1524.

[0091] 5) Enhance the driving ability of the PWM excitation control signal through the signal driving circuit to drive the IGBT half-bridge circuit of the excitation output circuit;

[0092] 6) The excitation output circuit adjusts the excitation voltage value of the excitation winding by controlling the on / off of the IGBT to generate an excitation current and adjust the output voltage of the generator.

[0093] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and all of these fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0094] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. An electrically excited control system for a generator, characterized in that, It includes a generator, a three-phase rectification and filtering circuit, a DC / DC circuit, a relay, and an excitation control circuit; The generator includes an excitation winding; the generator generates a three-phase sine voltage using residual magnetism, or receives an excitation voltage input to both ends of the excitation winding by the excitation control circuit to generate a three-phase sine voltage, and outputs the three-phase sine voltage to the three-phase rectification and filtering circuit; The three-phase rectification and filtering circuit receives the three-phase sine voltage input by the generator, converts the three-phase sine voltage into a DC bus voltage, and outputs the DC bus voltage to the DC / DC circuit and the excitation control circuit; The DC / DC circuit receives the DC bus voltage input by the three-phase rectification and filtering circuit. When the value of the DC bus voltage is less than the minimum input value of the DC / DC circuit, the DC / DC circuit does not work. When the value of the DC bus voltage is greater than or equal to the minimum input value of the DC / DC circuit, the DC / DC circuit performs a DC conversion on the DC bus voltage to obtain a converted DC voltage, and outputs the converted DC voltage to the relay and the excitation control circuit; The positive and negative output terminals of the relay are connected to both ends of the excitation winding, and the relay contacts are in a normally closed state; after the relay receives the converted DC voltage input by the DC / DC circuit, the relay contacts are disconnected to achieve the switching between the self-excitation mode and the he-excitation mode; the converted DC voltage is equal to the rated value of the relay coil; The excitation control circuit is powered by the converted DC voltage input by the DC / DC circuit; the excitation control circuit receives the DC bus voltage input by the three-phase rectification and filtering circuit, and generates an excitation voltage controlled by the value of the DC bus voltage. After the relay contacts are disconnected, the excitation control circuit outputs the excitation voltage to both ends of the excitation winding.

2. The electro-excitation control system for a generator according to claim 1, wherein The DC / DC circuit is a 90 - 350V wide-range input and 24V output DC / DC conversion circuit; The rated value of the relay coil is 24V; Both ends of the relay coil are connected to the output terminal of the DC / DC circuit, and the relay contacts are disconnected after the DC / DC circuit outputs a 24V DC voltage.

3. The electro-excitation control system for a generator according to claim 1, characterized in that, The excitation control circuit includes a voltage sampling circuit, a PWM control circuit, a signal driving circuit, and an excitation output circuit; The voltage sampling circuit receives the DC bus voltage input by the three-phase rectification and filtering circuit, performs an equal-proportion sampling on the DC bus voltage to obtain a DC bus voltage sampling value, and outputs the DC bus voltage sampling value to the PWM control circuit; The PWM control circuit generates a PWM excitation control signal according to the DC bus voltage sampling value, and outputs the PWM excitation control signal to the signal driving circuit; The signal driving circuit amplifies the PWM excitation control signal and outputs it to the excitation output circuit; The excitation output circuit generates an excitation voltage according to the amplified PWM excitation control signal, and the magnitude of the excitation voltage is related to the duty cycle of the PWM excitation control signal.

4. An electrically excited control system for a generator according to claim 3, characterized in that, The voltage sampling circuit adopts a resistor voltage division method to sample the DC bus voltage at a ratio of 1 / 140 to obtain a DC bus voltage sampling value.

5. The electro-excitation control system for a generator according to claim 3, characterized in that, The PWM control circuit includes a pulse width modulation chip SG1524 and peripheral circuits; The pulse-width modulation chip SG1524 integrates an error amplifier, a sawtooth wave generator, a signal comparator, and a reference voltage source internally; The peripheral circuit includes voltage-dividing resistors, a sawtooth wave frequency setting resistor, and a capacitor; The reference voltage source is divided by the voltage-dividing resistors to obtain the reference voltage of the error amplifier; The positive input terminal and the negative input terminal of the error amplifier respectively input the reference voltage of the error amplifier and the sampled value of the DC bus voltage. The error amplifier amplifies the error value between the reference voltage and the sampled value of the DC bus voltage to obtain a control signal, and outputs the control signal to the signal comparator; The sawtooth wave generator generates a sawtooth wave with a desired frequency by using the sawtooth wave frequency setting resistor and the capacitor, and outputs the sawtooth wave to the signal comparator; The signal comparator compares the control signal with the sawtooth wave to obtain a PWM excitation control signal.

6. The electro-excitation control system for a generator according to claim 3, characterized in that, The signal driving circuit includes a half-bridge driver IR2110; The high-end input signal HIN of the half-bridge driver IR2110 is the PWM excitation control signal output by the PWM control circuit, and the low-end input signal LIN is a stable high level.

7. An electrically excited control system for a generator according to claim 3, characterized in that, The excitation output circuit is a half-bridge circuit, including two IGBTs, which are the upper half-bridge tube and the lower half-bridge tube respectively; The amplified PWM excitation control signal output by the signal driving circuit controls the on-off of the upper half-bridge tube, and the lower half-bridge tube is in a constant-on mode.

8. An electro-excitation control system for a generator according to claim 3, characterized in that, The value of the excitation voltage is the product of the DC bus voltage and the duty cycle of the PWM excitation control signal; When the DC bus voltage increases, the duty cycle of the PWM excitation control signal decreases, and the excitation voltage decreases; when the DC bus voltage decreases, the duty cycle of the PWM excitation control signal increases, and the excitation voltage increases.

9. A field excitation control system for a generator according to claim 1, wherein The three-phase rectifier filter circuit includes a three-phase uncontrolled bridge rectifier circuit and a capacitor filter circuit; [[ID= 10. A method for electrically exciting control of a generator, characterized in that, ​ ​ ​ ​

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