A control method and control system of a rectifier generator set

Abstract

The application discloses a control method and a control system of a rectifier generator set, and the control method comprises the following steps: collecting an alternating voltage signal output by a main generator and processing the alternating voltage signal to determine the rotating speed of the main generator set; obtaining a rectifier output direct current instruction through a rotating speed PI regulator after the rotating speed is subtracted from a reference rotating speed, and outputting the rectifier output direct current instruction after limiting amplitude processing through current limiting amplitude; subtracting a rectifier output direct current instruction after the limiting amplitude processing from a direct current signal output by the rectifier, and then outputting a PWM pulse wave with an adjustable duty cycle through a current PI regulator after the subtraction, so as to control the output of a Buck chopper circuit. The application can effectively solve the problem of energy circulation when multiple generator sets are operated in parallel.

Description

Technical Field

[0001] This invention belongs to the technical field of rectifier generator sets, and more specifically, relates to a control method and control system for rectifier generator sets. Background Technology

[0002] Rectifier generator sets are widely used in DC power systems and mainly consist of an exciter, main generator, AC-DC rectifier, excitation power supply, excitation power amplifier, and excitation control system. They use a Stirling engine as the prime mover, and the main generator output is rectified by the AC-DC rectifier to supply DC power to the batteries. The exciter armature converts the mechanical energy provided by the prime mover into electrical energy and supplies power to the main generator's excitation winding through the rotating rectifier. The excitation power supply powers the excitation power amplifier. The excitation control system uses the main generator's speed as the outer loop control target and the excitation current as the inner loop control target, controlling the power amplifier to ensure stable generator speed and DC output voltage.

[0003] When multiple generator sets (two or more) are operated in parallel, a reactor is usually connected in parallel on the busbar for filtering to stabilize the bus voltage. However, when there is a disturbance in the output voltage of one of the generators, the DC output of the AC-DC rectifier lags behind the armature reaction electromotive force of the exciter due to the suppression effect of the reactor on the disturbance. That is, their relationship is nonlinear. At this time, if the excitation current is still used as the inner loop control target, the excitation current PI loop cannot accurately and quickly track the fluctuation of the output DC, which will cause energy to form a circulating current between the two generator sets, making the output DC voltage unstable. Long-term operation will affect the battery life. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a control method and control system for rectifier generator sets, which aims to solve the problem of energy circulation when multiple generator sets are connected in parallel.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a control method for a rectifier generator set, the rectifier generator set including an exciter, a main generator, an AC-DC rectifier, an excitation power supply, and an excitation power amplifier, wherein the excitation power amplifier employs a Buck chopper, and the control method includes the following steps:

[0006] (1) Collect the AC voltage signal output by the main generator and process the AC voltage signal to determine the speed n of the main generator set;

[0007] (2) Compare the rotational speed n with the reference rotational speed n ref After the difference is calculated, the DC command I output from the rectifier is obtained through the speed PI regulator. a-cmd Then, after limiting the amplitude, the output is processed;

[0008] (3) The DC command I output by the rectifier after the amplitude limiting process a-cmd With the DC signal I output by the rectifier a The difference is calculated, and then the output DC deviation after the difference is passed through a current PI regulator to output an adjustable duty cycle PWM pulse wave, which is used to control the output of the Buck chopper circuit.

[0009] In one embodiment, in step (2), the reference rotational speed n ref Determined based on the rated operating speed of the main generator.

[0010] In one embodiment, in step (2), the method for determining the proportional and integral coefficients in the speed PI regulator is as follows: first, determine the proportional coefficient K of the speed PI regulator. p1 First, the integral coefficient K i1 Set it to 0 to make it a pure proportional control, then set the speed specification value to 60% to 70% of the rated speed, K p1 Start from 0 and gradually increase until the speed waveform oscillates; then reverse the process, starting from the proportional coefficient K at this point. p1 Gradually decrease the speed until the speed oscillation disappears, and record the proportional coefficient K at this point. p1 proportionality coefficient K p1 The confirmed value is 60% to 70% of the current value; after the proportionality coefficient is determined, a relatively large integral coefficient K is set. i1 Then gradually decrease K i1 Continue this process until the rotational speed begins to oscillate, then reverse the process and gradually increase K. i1 Continue until the oscillation disappears, and record the integral coefficient K at this point. i1 Integral coefficient K i1 The confirmed value is 150% to 180% of the current value.

[0011] In one embodiment, in step (3), the method for determining the proportional and integral coefficients in the current PI regulator is as follows: first, determine the proportional coefficient K of the current PI regulator. p2 First, the integral coefficient K i2 Set it to 0 to make it a pure proportional adjustment, then set the current specification value to 60% to 70% of the rated current, K p2 Start from 0 and gradually increase until the current waveform oscillates; then reverse the process, starting from the proportional coefficient K at this point. p2 Gradually decrease the current until the current oscillation disappears, and record the proportional coefficient K at this point. p2 proportionality coefficient K p2 The confirmed value is 60% to 70% of the current value; after the proportionality coefficient is determined, a relatively large integral coefficient K is set. i2Then gradually decrease K i2 Continue this process until the current oscillates, then reverse the process, gradually increasing K. i2 Until the oscillation disappears, record the K value at this point. i2 The confirmed value of the integral coefficient is 150% to 180% of the current value.

[0012] In one embodiment, step (1), the step of processing the AC voltage signal to determine the rotational speed n of the main generator set, specifically includes:

[0013] (a) Using a voltage sensor to convert the AC voltage signal into an AC current signal I of the same frequency. m And by measuring the resistance, the AC current signal I is converted. m Converted to a sinusoidal voltage signal U m ;

[0014] (b) Using a hysteresis comparator circuit, the sinusoidal voltage signal U is... m Shaped into an AC current signal I with a frequency m times that of the signal. m A square wave signal S with a frequency of [frequency missing].

[0015] (c) The frequency of the square wave signal S is measured using the capture pin of the processor, and the rotational speed n of the main generator set is calculated in real time based on the frequency of the square wave signal S and the multiplication factor m.

[0016] In one embodiment, in step (1), the rotational speed n of the main generator set is:

[0017] n = m60p / f s

[0018] In the formula, p represents the number of pole pairs of the main generator; f s This indicates the frequency of the square wave signal S.

[0019] Secondly, the present invention provides a control system for a rectifier generator set, the rectifier generator set including an exciter, a rotating rectifier, a main generator, an AC-DC rectifier, an excitation power supply, and an excitation power amplifier, wherein the excitation power amplifier employs a Buck chopper, and the control system includes:

[0020] The sampling circuit is used to convert the AC voltage signal output by the main generator into an AC current signal I of the same frequency. m and the alternating current signal I m Converted to a sinusoidal voltage signal U m ;

[0021] Hysteresis comparator circuit is used to convert the sinusoidal voltage signal U m Shaped into an AC current signal I with a frequency m times that of the signal.m A square wave signal S with a frequency of [frequency missing].

[0022] The processing circuit is used to measure the frequency of the square wave signal S, and simultaneously calculate the rotational speed n of the main generator set in real time based on the frequency of the square wave signal S and the frequency multiplier m; it is also used to execute the following process: comparing the rotational speed n with the reference rotational speed n ref After the difference is calculated, the DC command I output from the rectifier is obtained through the speed PI regulator. a-cmd The output is then subjected to amplitude limiting; the DC command I of the rectifier output after amplitude limiting is then applied. a-cmd With the DC signal I output by the rectifier a * The difference is calculated, and then the output DC deviation after the difference is passed through a current PI regulator to output an adjustable duty cycle PWM pulse wave, which is used to control the output of the Buck chopper circuit.

[0023] In one embodiment, the processing circuit employs a DSP processor.

[0024] The control method and control system for rectifier generator sets provided by this invention adopt a dual closed-loop PI control method consisting of an outer speed loop and an inner DC output current loop. The excitation output is controlled by using the DC output current as the inner loop control quantity. This method can not only meet the operating conditions of a single unit, but also effectively ensure the stability of the generator set's speed and DC output voltage under the condition of multiple units operating in parallel. Attached Figure Description

[0025] Figure 1 The excitation electromotive force E0 and the reaction electromotive force E provided by this invention a and air gap electromotive force E δ Vector relationship diagram;

[0026] Figure 2 The present invention provides that when the excitation electromotive force E0 is 0, the excitation electromotive force E0 and the reaction electromotive force E a and air gap electromotive force E δ Vector relationship diagram;

[0027] Figure 3 This is a control block diagram of a control method for a rectifier generator set provided in an embodiment of the present invention;

[0028] Figure 4 This is a waveform diagram of the output DC current under disturbance conditions using a traditional excitation control strategy.

[0029] Figure 5 This is a waveform diagram of the DC current output by the control method provided by the present invention under disturbance conditions.

[0030] Figure 6This is a schematic diagram of the control system of a rectifier generator set provided in an embodiment of the present invention; Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] To address the energy circulation issue when multiple generator sets are operating in parallel, it is necessary to first analyze the output voltage U, output current I, and excitation current I of the main generator in the rectifier generator set. fe The relationship is analyzed using the following method:

[0033] Assuming the generator set is in steady state, the excitation electromotive force in the exciter winding is E0, and the reaction electromotive force of the main generator armature is E. a The air gap electromotive force is E δ According to the voltage vector relationship, we can obtain:

[0034] U = E δ =E0+E a

[0035] If the stator resistance and stator leakage reactance of the main generator are ignored, the voltage vector relationship is as follows: Figure 1 As shown, the expression for the excitation electromotive force E0 can be obtained according to the law of cosines:

[0036]

[0037] According to the analysis, when the main generator power factor angle When the angle is 90°, the excitation electromotive force E0 of the generator set is at its maximum in steady state. At this time, E0 and E a and E δ The vector relationship is as follows Figure 2 As shown, we can obtain:

[0038] E 0max =U+E a (1)

[0039] When a single rectifier generator set operates independently, the excitation current I fe It is directly proportional to the excitation electromotive force E0. Assume the open-circuit voltage coefficient of the main generator is K. f Output DC I a The reaction electromotive force E of the main generator armature a They are directly proportional, assuming the short-circuit current coefficient of the main generator is K. a Then, the above equation (1) can be simplified to:

[0040]

[0041] When multiple generator sets (two or more) are operating in parallel, a reactor is typically connected in parallel with the busbar for filtering to stabilize the bus voltage. However, if there is a disturbance in the output voltage of one of the generators, the reactor's suppression effect on the disturbance will cause the output DC I... a Lagging behind the armature reaction electromotive force E a That is, they are nonlinear relationships, and equation (2) above does not hold. At this time, if the excitation current is still used as the inner loop control target, the excitation current PI loop cannot accurately and quickly track the fluctuations of the output DC, resulting in the formation of a circulating current between the two generators, which makes the output DC voltage unstable and will affect the battery life after long-term operation.

[0042] Assume the equivalent impedance of the reactor connected in parallel on the busbar is K. r Equation 2 can be changed to:

[0043]

[0044] From equation (3), it can be seen that the excitation current I fe With DC output current I a The relationship is linear. The DC output current is used as the inner loop control quantity to control the excitation output. The DC current PID can be used to counteract the influence of external disturbances and make the output DC current stable.

[0045] Therefore, this invention improves the control strategy of the traditional excitation control system, and the improved control block diagram is as follows. Figure 3 As shown, by Figure 3 As can be seen, the control method for the rectifier generator set provided by the present invention includes steps S10 to S30, which are detailed below:

[0046] S10, acquires the AC voltage signal U output by the main generator and the DC signal I output by the rectifier. a * The AC voltage signal U is processed to determine the rotational speed n of the main generator set.

[0047] In step S10, as Figure 2 As shown, the method for processing the AC voltage signal U to determine the speed n of the main generator set can be specifically as follows: (1) Use a voltage sensor to convert the AC voltage signal into an AC current signal I of the same frequency. s And by measuring the resistance, the AC current signal I is converted. m Converted to a sinusoidal voltage signal U m (2) Then, using a hysteresis comparator circuit commonly used in this field, the sinusoidal voltage signal U is converted into a signal. m Shaped into an AC current signal I with a frequency of m times.s (3) Finally, the frequency of the square wave signal S is measured using the capture pin of the processor, and the rotational speed n of the main generator set is calculated in real time based on the frequency of the square wave signal S and the multiplication factor m.

[0048] Specifically, the processor calculates the main generator speed n in real time based on the frequency of the square wave signal S and its multiple m. The principle is as follows: Since the AC voltage signal U and the square wave signal S have the same frequency, and the square wave signal S has a frequency that is m times that of the AC current signal I... m The frequency f of the square wave signal S is... s The frequency f of the AC voltage signal U satisfies: f = f s / m; then, based on the relationship between the generator speed and the frequency f of its output AC voltage signal: n = 60p / f, the speed n of the synchronous AC generator can be calculated, i.e., n = m60p / f s , where p represents the number of pole pairs of the main generator.

[0049] It should be noted that, in order to ensure the reliability of frequency measurement, the AC voltage input to the reference terminal of the hysteresis comparator circuit provided in this embodiment must be greater than the AC voltage of the main generator; otherwise, the hysteresis comparator circuit cannot output a square wave signal.

[0050] S20, compare the rotational speed n with the reference rotational speed n ref The speed deviation is obtained by subtraction, and then the speed deviation is used to obtain the DC output command I of the rectifier through the speed PI regulator. a-cmd The output is then limited by current limiting. The reference rotational speed n... ref Determined based on the rated operating speed of the main generator.

[0051] The method for determining the proportional and integral coefficients in the speed PI regulator provided in this embodiment is as follows: First, determine the proportional coefficient K of the speed PI regulator. p1 First, the integral coefficient K i1 Set it to 0 to make it a pure proportional control, then set the speed specification value to 60% to 70% of the rated speed, K p1 Starting from 0, gradually increase the coefficient until the speed waveform begins to oscillate. Then, conversely, from this point, increase the proportional coefficient K... p1 Gradually decrease the speed until the speed oscillation disappears, and record the proportional coefficient K at this point. p1 proportionality coefficient K p1 The confirmed value is 60% to 70% of the current value. After determining the proportionality coefficient, a relatively large integral coefficient K is set. i1 Then gradually decrease K i1 Continue this process until the rotational speed begins to oscillate, then reverse the process and gradually increase K. i1Continue until the oscillation disappears, and record the integral coefficient K at this point. i1 Integral coefficient K i1 The confirmed value is 150% to 180% of the current value.

[0052] S30 outputs DC command I from the rectifier after the limiting process. a-cmd With the DC signal I output by the rectifier a * The difference is calculated, and the resulting DC deviation is then passed through a current PI regulator to output a PWM pulse wave with an adjustable duty cycle. This PWM pulse wave is used to control the output of the Buck chopper circuit.

[0053] In step S30, the method for determining the proportional and integral coefficients in the current PI regulator is as follows: First, determine the proportional coefficient K of the current PI regulator. p2 First, the integral coefficient K i2 Set it to 0 to make it a pure proportional adjustment, then set the current specification value to 60% to 70% of the rated current, K p2 Starting from 0, gradually increase the coefficient until the current waveform oscillates. Then, conversely, from this point, increase the proportionality coefficient K... p2 Gradually decrease the current until the current oscillation disappears, and record the proportional coefficient K at this point. p2 proportionality coefficient K p2 The confirmed value is 60% to 70% of the current value. After determining the proportionality coefficient, a relatively large integral coefficient K is set. i2 Then gradually decrease K i2 Continue this process until the current oscillates, then reverse the process, gradually increasing K. i2 Until the oscillation disappears, record the K value at this point. i2 The confirmed value of the integral coefficient is 150% to 180% of the current value.

[0054] Figure 4 and Figure 5 The waveforms of the traditional excitation control strategy and the control method provided by this invention under the same disturbance are shown below. Figure 4 and Figure 5 It can be seen that the control method provided by this invention can effectively solve the problem of voltage fluctuation when multiple machines are running in parallel.

[0055] The control method for the rectifier generator set provided in this embodiment adopts a dual closed-loop PI control method with an outer speed loop and an inner DC output current loop. The excitation output is controlled by using the DC output current as the inner loop control quantity. This method can not only meet the operating conditions of a single unit, but also effectively ensure the stability of the generator set's speed and DC output voltage under the condition of multiple units operating in parallel.

[0056] Based on the same inventive concept, the present invention also provides a control system for a rectifier generator set, such as... Figure 6 As shown, the control system includes a sampling circuit, a hysteresis comparison circuit, and a processing circuit.

[0057] The sampling circuit can employ a voltage sensor and a measuring resistor. The voltage sensor is used to convert the AC voltage signal output by the main generator into an AC current signal I of the same frequency. m The measuring resistor is used to convert the alternating current signal I... m Converted to a sinusoidal voltage signal U m .

[0058] Hysteresis comparator circuit is used to convert sinusoidal voltage signal U m Shaped into an AC current signal I with a frequency of m times. m A square wave signal S with a specific frequency.

[0059] The processing circuit, specifically a DSP processor, is used to measure the frequency of the square wave signal S using its capture pin, and simultaneously calculate the rotational speed n of the main generator set in real time based on the frequency of the square wave signal S and its harmonic multiplier m. It also performs the following process: comparing the rotational speed n with a reference rotational speed n... ref After differential calculation, the DC output command I of the rectifier is obtained through the speed PI regulator. a-cmd The current is used to limit the output of the rectifier, and then the output is limited; the DC command I of the limited rectifier is then used to output the rectifier. a-cmd With the DC signal I output by the rectifier a * The difference is calculated, and then the DC deviation of the output after the difference is passed through the current PI regulator to output an adjustable duty cycle PWM pulse wave. The PWM pulse wave is used to control the output of the Buck chopper circuit.

[0060] The control system of the rectifier generator set provided in this embodiment adopts a dual closed-loop PI control method with an outer speed loop and an inner DC output current loop. The excitation output is controlled by using the DC output current as the inner loop control quantity. This method can not only meet the operating conditions of a single unit, but also effectively ensure the stability of the generator set's speed and DC output voltage under the condition of multiple units operating in parallel.

[0061] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a rectifier generator set, characterized in that, The rectifier generator set includes an exciter, a main generator, an AC-DC rectifier, an excitation power supply, and an excitation power amplifier. The excitation power amplifier uses a Buck chopper. The control method includes the following steps: (1) Collect the AC voltage signal output by the main generator and process the AC voltage signal to determine the speed of the main generator set. n ; (2) Adjust the rotation speed n With reference speed n ref After differential calculation, the DC output command of the rectifier is obtained through the speed PI regulator. I a-cmd Then, after limiting the amplitude, the output is processed; (3) Output DC command from the rectifier after limiting. I a-cmd DC signal output by rectifier I a The difference is calculated, and then the output DC deviation after the difference is passed through the current PI regulator to output an adjustable duty cycle PWM pulse wave. The PWM pulse wave is used to control the output of the Buck chopper circuit, thereby effectively ensuring the stability of the generator set speed and DC output voltage under the condition of multiple generators in parallel.

2. The control method for a rectifier generator set according to claim 1, characterized in that, In step (2), the reference rotational speed n ref Determined based on the rated operating speed of the main generator.

3. The control method for a rectifier generator set according to claim 1 or 2, characterized in that, In step (2), the method for determining the proportional and integral coefficients in the speed PI regulator is as follows: First, determine the proportional coefficient of the speed PI regulator. K p1 First, the integral coefficients K i1 Set it to 0 to make it a pure proportional control, and then set the speed specification value to 60%~70% of the rated speed. K p1 Start from 0 and gradually increase until the speed waveform oscillates; then reverse the process and increase the proportional coefficient from this point. K p1 Gradually decrease the speed until the speed oscillation disappears, and record the proportional coefficient at this point. K p1 proportionality coefficient K p1 The confirmed value is 60% to 70% of the current value; after the proportional coefficient is determined, a relatively large integral coefficient is set. K i1 Then gradually decrease K i1 Continue until the rotational speed oscillates, then reverse the process and gradually increase the speed. K i1 Continue until the oscillations disappear, and record the integral coefficient at this point. K i1 Integral coefficient K i1 The confirmed value is 150% to 180% of the current value.

4. The control method for a rectifier generator set according to claim 1, characterized in that, In step (3), the method for determining the proportional and integral coefficients in the current PI regulator is as follows: First, determine the proportional coefficient of the current PI regulator. K p2 First, the integral coefficients K i2 Set it to 0 to make it a pure proportional adjustment, and then set the current specification value to 60%~70% of the rated current. K p2 Start from 0 and gradually increase until the current waveform oscillates; then reverse the process, starting from the proportional coefficient at this point. K p2 Gradually decrease the current until the current oscillation disappears, and record the proportional coefficient at this point. K p2 proportionality coefficient K p2 The confirmed value is 60% to 70% of the current value; after the proportional coefficient is determined, a relatively large integral coefficient is set. K i2 Then gradually decrease K i2 Until the current oscillates, then the process is reversed, gradually increasing... K i2 Record this moment until the oscillation disappears. K i2 The confirmed value of the integral coefficient is 150% to 180% of the current value.

5. The control method for a rectifier generator set according to claim 1, characterized in that, In step (1), the AC voltage signal is processed to determine the speed of the main generator set. n The steps are as follows: (a) Using a voltage sensor to convert the AC voltage signal into an AC current signal of the same frequency. I m And by measuring the resistance, the AC current signal is converted. I m Convert to sinusoidal voltage signal U m ; (b) Using a hysteresis comparator circuit to convert the sinusoidal voltage signal U m Shaping to frequency m The alternating current signal is doubled. I m Square wave signal of frequency S ; (c) Using the processor's capture pin to capture the square wave signal S The frequency is measured, and the square wave signal is used as a reference. S Frequency and harmonics m The rotational speed of the main generator set is calculated in real time. n .

6. The control method for a rectifier generator set according to claim 5, characterized in that, In step (1), the rotational speed of the main generator set n for: n=m60p / f s In the formula, p Indicates the number of pole pairs of the main generator; f s The square wave signal S The frequency.

7. A control system for a rectifier generator set, characterized in that, The rectifier generator set includes an exciter, a rotating rectifier, a main generator, an AC-DC rectifier, an excitation power supply, and an excitation power amplifier. The excitation power amplifier uses a Buck chopper. The control system includes: The sampling circuit is used to convert the AC voltage signal output by the main generator into an AC current signal of the same frequency. I m and the alternating current signal I m Convert to sinusoidal voltage signal U m ; Hysteresis comparator circuit is used to convert the sinusoidal voltage signal U m Shaping to frequency m The alternating current signal is doubled. I m Square wave signal of frequency S ; Processing circuit for measuring the square wave signal S The frequency, and simultaneously based on the square wave signal S Frequency and harmonics m The rotational speed of the main generator set is calculated in real time. n It is also used to perform the following process: [the process involves adjusting the rotational speed]. n With reference speed n ref After differential calculation, the DC output command of the rectifier is obtained through the speed PI regulator. I a-cmd The output is then subjected to amplitude limiting; the DC command is then output from the rectifier after amplitude limiting. I a-cmd DC signal output by rectifier I a * The difference is calculated, and then the output DC deviation after the difference is passed through the current PI regulator to output an adjustable duty cycle PWM pulse wave. The PWM pulse wave is used to control the output of the Buck chopper circuit, thereby effectively ensuring the stability of the generator set speed and DC output voltage under the condition of multiple generators in parallel.

8. The control system of the rectifier generator set according to claim 7, characterized in that, The processing circuit uses a DSP processor.

Images