Method for improving stability of voltage regulator of synchronous generator with small duty cycle and voltage regulator circuit

Abstract

The present invention relates to a method for improving the stability of a voltage regulator of a synchronous generator with a small duty cycle and a voltage regulator circuit. In the case of a small duty cycle, a method for connecting a stabilizing resistor in series in the voltage regulator is used. Through speed judgment and control, a stabilizing resistor is inserted when the variable frequency AC generator is at a high speed. The magnitude of the excitation current is limited by voltage division, and the superposition of the resistor voltage division part and the excitation machine winding voltage division part is equivalent to amplifying the small duty cycle, thereby improving the stability of the system loop. Through verification by an existing variable frequency motor, the system excitation current can maintain the continuity of the current compared to when no current is taken, and the unloading fluctuation rate is significantly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation electrical design, and relates to a method for improving the stability of a voltage regulator of a small duty cycle synchronous generator and a voltage regulator circuit. Background Art

[0002] With the development of the application of aviation variable frequency power system, the application of wide speed range variable frequency AC power generation system is becoming more and more extensive. The variable frequency AC power generation system generally adopts the three-stage synchronous AC generator with high reliability and wide use. However, the excitation current of the synchronous AC generator is small at high speed and large at low speed. Its excitation is generally carried out by direct conversion into DC by permanent magnet machine. The voltage is low at low speed and high at high speed. The PWM control leads to a very small PWM duty cycle at high speed, sometimes even less than 2%, which leads to poor stability in system control and easy problems of discontinuous excitation current and large modulation of power generation voltage. Therefore, it is generally necessary to repeatedly analyze the motor excitation parameters and permanent magnet machine parameters during design, and determine the reasonable parameters after optimization to ensure the rationality of the excitation PWM duty cycle. However, due to design deviation or material magnetic properties, it is often difficult to improve the motor after processing. It needs to be improved from the control perspective. The optimization and improvement of the small duty cycle synchronous generator voltage regulator is extremely necessary.

[0003] In order to solve the problems of discontinuous excitation current and large modulation of generated voltage caused by variable frequency AC power generation system, methods such as adding integral circuits can improve the system regulation characteristics. However, overshoot may easily occur during the voltage interruption recovery process, and the scope of application is slightly insufficient, making it difficult to meet the requirements of relevant standards for the characteristic indicators of power generation systems. Summary of the invention

[0004] Technical issues to be solved

[0005] In order to avoid the shortcomings of the prior art, the present invention provides a method for improving the stability of a small duty cycle synchronous generator voltage regulator and a voltage regulator circuit, and a method for reducing the current provided to the excitation winding of a variable frequency AC generator by voltage division.

[0006] Technical Solution

[0007] A method for improving the stability of a voltage regulator of a synchronous generator with a small duty cycle, characterized in that: under low speed conditions, all the rectified excitation voltage is supplied to the exciter, and PWM control is performed by the power tube 7 to achieve large duty cycle control in the low speed working state, thereby ensuring that the excitation current is sufficient; when in a high speed working state, part of the rectified excitation voltage is supplied to the exciter, the current of the permanent magnet machine rectified voltage passing through the exciter winding is limited, and the energy of the small duty cycle is controlled by voltage division control, so that the duty cycle is amplified, thereby ensuring the stability of the system loop.

[0008] A voltage regulator circuit for realizing the method for improving the stability of a voltage regulator of a synchronous generator with a small duty cycle, comprising a generator voltage sensitive signal 1, a conditioning conversion circuit 2, a reference voltage circuit 3, a PID adjustment circuit 4, a comparison circuit 5, a drive circuit 6, a power tube 7, an internal power supply 8 for power conversion and a permanent magnet machine rectifier circuit 9; characterized in that it also comprises a through-control power tube 11, a stabilizing resistor 10 and a speed sensitive control and drive 13; the through-control power tube 11 and the stabilizing resistor 12 are connected in parallel between the permanent magnet machine rectifier circuit 9 and the power tube 7, and the speed sensitive control and drive 13 is an input signal of the through-control power tube 11; under low speed conditions, the through-control power tube 11 turns on the stabilizing resistor 10 to short-circuit, and directly performs excitation regulation; when in a high speed working state, the through-control power tube 11 is turned off, the stabilizing resistor 12 limits the excitation current, and the energy of the small duty cycle is controlled by voltage division control, so that the duty cycle is amplified to ensure the stability of the system loop.

[0009] The input signal of the through-control power tube 11 adopts the output signal of the low-speed through-control circuit.

[0010] The through-control power tube 11 adopts a low-speed through-control tube V3.

[0011] The low speed direct control tube V3 is a power tube with the same parameters as V1.

[0012] The stabilizing resistor 12 is RJ1 and is set within 10 ohms.

[0013] Beneficial Effects

[0014] The present invention proposes a method for improving the stability of a voltage regulator of a synchronous generator with a small duty cycle and a voltage regulator circuit. In the case of a small duty cycle, a method for connecting a stabilizing resistor in series in the voltage regulator is used. Through speed judgment and control, a stabilizing resistor is inserted when the variable frequency AC generator is at a high speed. The excitation current is limited by voltage division, and the superposition of the resistor voltage division part and the excitation machine winding voltage division part is equivalent to amplifying the small duty cycle, thereby improving the stability of the system loop. Through verification by existing variable frequency motors, the system excitation current can maintain the continuity of the current compared to when no action is taken, and the unloading fluctuation rate is significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 :Present technology voltage regulation circuit

[0016] Figure 2 : Schematic diagram of the improved voltage regulator of the present invention

[0017] Figure 3 :The present invention improves the voltage regulator circuit

[0018] Figure 4 :Excitation current and voltage waveform DETAILED DESCRIPTION

[0019] The present invention will now be further described with reference to the embodiments and the accompanying drawings:

[0020] Existing voltage regulator principle Figure 1 As shown, in the general circuit principle block diagram, the voltage regulator includes a generator voltage sensitive signal 1, a conditioning conversion circuit 2, a reference voltage circuit 3, a PID adjustment circuit 4, a comparison circuit 5, a drive circuit 6, a power tube 7, an internal power supply for power conversion 8, a permanent magnet machine rectifier circuit 9, and a freewheeling tube 10.

[0021] The present invention Figure 1 Based on the improved voltage regulation technology, such as Figure 2 , add direct control power tube 11, stabilizing resistor 12, speed sensitive control and drive 13 and other parts. During operation, the stabilizing resistor 12 is connected in parallel with the through-control power tube 11, and the speed-sensitive control and drive 13 determines whether the generator is at a low speed (large duty cycle condition) or a high speed (small duty cycle condition) according to the speed of the variable frequency AC generator. When in a low speed working state, the through-control power tube 11 is turned on and is in a full-on state, so that the rectified excitation voltage is all supplied to the exciter, and the power tube 7 performs PWM control to achieve a large duty cycle control in a low speed working state, ensuring that the excitation current is sufficient; when in a high speed working state, the through-control power tube 11 is turned off and is in a full-off state, so that the rectified excitation voltage is all supplied to the exciter through the stabilizing resistor 12. Since the rectified voltage of the permanent magnet machine passes through the stabilizing resistor 12 and the exciter winding, the current is limited within a certain range. By reasonably setting the size of the stabilizing resistor 12, the excitation current can be limited, which is equivalent to controlling the energy of the small duty cycle by voltage division control, so that the duty cycle is amplified, and the stability of the system loop is ensured.

[0022] Figure 3 In order to improve the voltage regulator circuit, the PWM control part includes the generator voltage sensitive signal 1, the conditioning conversion circuit 2, the reference voltage circuit 3, the PID adjustment circuit 4, the comparison circuit 5, the drive circuit 6 and other circuits. The permanent magnet machine rectifier circuit 9 is V4~V9, the power tube 7 is V1, the freewheeling tube 10 is V2, the speed sensitive control and drive 13 is the output signal of the low-speed direct control circuit, the stabilizing resistor 12 is RJ1, and the direct control power tube 11 is V3.

[0023] Among them, V1 is the power tube of the voltage regulator, V2 is the freewheeling diode, V3 is the low-speed direct control tube, RJ1 is the stabilizing resistor, R j is the excitation winding resistance, L j is the inductance of the exciting winding, E d is the DC voltage output by the PMG three-phase full-wave rectifier, E c is the DC voltage at the positive terminal of the excitation winding.

[0024] When V1 is in an ideal switching state (distributed parameters and tube voltage drop are not considered, that is, V 1d For an ideal square wave, the voltage U across D and S of V1 is DS =E d ,I DS0 =0), excitation current I j Waveform Figure 4 As shown (T is the switching period of PWM control, V1 is on for ton, and V1 is off for t off , I j2 is the maximum current when turned on, I j1 is the maximum current when shutting down).

[0025] At the opening time t on Inside, the power tube V1 is turned on, the exciting winding is connected to the power supply, and the exciting current rises. The circuit equation is:

[0026] I j( R j+ RJ 1) +L j d j / dt=E d (1-1)

[0027] Ec=E d -I j RJ1 (1-2)

[0028] In the formula, R j , L j is the internal resistance and inductance of the excitation winding. Since the maximum value of the excitation current I jM =E d / (R j+ RJ1), time constant τ of the excitation circuit j =L j / R j . In general, the time constant of the excitation circuit is T<<τ j By solving the differential equation, we can get the average excitation current

[0029]

[0030] In the formula, is the conduction ratio.

[0031] It can be concluded that

[0032] R j , RJ1, and T remain unchanged. Increasing RJ1 is equivalent to amplifying the duty cycle of the control. By extending the duty cycle, the effective proportional range of the control regulation characteristics under small duty cycle is expanded, and the system stability is improved.

[0033] Under low speed conditions, through speed judgment control, V3 is turned on, resistor RJ1 is short-circuited, and excitation adjustment is directly performed. Speed ​​judgment control can be performed through frequency detection comparison circuit or software control method, which will not be described here.

[0034] In the circuit, RJ1 is generally set within 10 ohms, and the example setting is 3.3 ohms. The excitation working current of the variable frequency AC generator operates at about 1A. RJ1 selects a 5W power resistor, and appropriate heat dissipation measures are taken inside the voltage regulator to meet the requirements; V3 generally selects a power tube with the same parameters as V1; the low-speed direct control circuit adopts software comparison control signal setting.

Claims

1. A voltage regulator circuit for improving a small duty cycle synchronous generator, comprising a generator voltage sensitive signal [1], a conditioning conversion circuit [2], a reference voltage circuit [3], a PID regulation circuit [4], a comparison circuit [5], a drive circuit [6], a power tube [7], a power conversion internal power supply [8] and a permanent magnet machine rectifier circuit [9]; characterized in that The invention also includes a through control field effect tube [11], a stabilizing resistor [12] and a speed sensitive control and drive [13]. The through control field effect tube [11] adopts a low speed through control tube V3, and the input signal adopts the output signal of the low speed through control circuit; the through control field effect tube [11] and the stabilizing resistor [12] are connected in parallel between the permanent magnet machine rectifier circuit [9] and the power tube [7], and the speed sensitive control and drive [13] is the input signal of the through control field effect tube [11]; the excitation adopts the permanent magnet machine to directly convert into a direct current mode, under the condition of low speed, the through control field effect tube [11] turns on the stabilizing resistor [10] to short-circuit, and directly adjusts the excitation; when in a high speed working state, the through control field effect tube [11] turns off, the stabilizing resistor [12] limits the excitation current, and the energy of the small duty cycle is controlled by voltage division control, so that the duty cycle is amplified to ensure the stability of the system loop.

2. A method for improving voltage stabilization of a small duty cycle synchronous generator voltage regulator circuit according to claim 1, characterized in that: The excitation adopts the method of directly converting the permanent magnet machine into direct current. In view of the characteristics of low voltage at low speed and high voltage at high speed, under low speed conditions, the rectified excitation voltage is fully supplied to the excitation machine, and PWM control is performed by the power tube [7] to achieve large duty cycle control in the low speed working state; when in the high speed working state, the rectified excitation voltage is partially supplied to the excitation machine, and the current of the permanent magnet machine rectified voltage passing through the excitation machine winding is limited, and the energy of the small duty cycle is controlled by voltage division control, so that the duty cycle is amplified to ensure the stability of the system loop.

3. The voltage regulator for improving a synchronous generator with a small duty cycle according to claim 1, characterized in that: The low speed direct control tube V3 is a power tube with the same parameters as V1.

4. The voltage regulator for improving a synchronous generator with a small duty cycle according to claim 1, characterized in that: The stabilizing resistor [12] is RJ1 and is set within 10 ohms.

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