Oscillation suppression method for suppressing relay pre-charging protection circuit

Abstract

The invention discloses an oscillation suppression method for suppressing a relay pre-charging protection circuit, and the method comprises the steps: introducing a Posicast feedforward controller in a PWM control circuit, and carrying out the suppression and weakening of oscillation. At the switching moment of the relay, the current at the alternating current side is increased instantly, the Posicast feedforward controller divides an input signal into two sub-signals with different amplitudes according to a time interval, the two sub-signals are sent to a controlled object, and then responses are superposed to eliminate the oscillation problem of the system. Current impact and oscillation caused by relay switching can be effectively eliminated, the stability of the pre-charging protection circuit is remarkably improved, a relay switching event can be quickly responded, and the system recovery time is shortened.

Description

Technical Field

[0001] The invention relates to a relay pre-charging protection circuit, and in particular to an oscillation suppression method for suppressing the relay pre-charging protection circuit. Background Art

[0002] In modern power electronic equipment, relay pre-charge protection circuits are widely used to protect power components from damage caused by instantaneous current surges during startup. However, when the relay is closed, instantaneous current surges and oscillations will occur in the circuit, which will not only affect the stability and performance of the system, but may also cause component damage. The current pre-charge protection method usually adopts simple filtering technology, but there are still problems such as slow response and poor suppression effect. In order to solve the problem of current surges in PFC when the relay is switched on, Posicast control is introduced in the PWM control circuit to suppress the surges.

[0003] like Figure 1 As shown, it is a bridgeless PFC topology with EMI filter.

[0004] Existing technology and defects:

[0005] The existing pre-charge protection circuit technology mainly uses a relay in parallel with a resistor. At the moment the power is turned on, the current limiting resistor is used to suppress the impact current. Although this method is simple and easy to implement, problems such as oscillation at the moment of relay switching still exist. If the current impact problem at the moment of relay switching cannot be solved, it may cause component damage or system instability. And the oscillation problem in the switching process will also affect the system performance, especially in the application of high-frequency signals. In addition, this pre-charge protection technology has a slow response speed and cannot quickly respond to current impacts and changes in system status.

[0006] When the circuit cuts off the relay, the current changes as follows Figure 2 As shown, it is necessary to consider adding protection measures to suppress surge current, oscillation and other problems at the moment of switching off the relay.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The object of the present invention is to provide a method for suppressing oscillation of a relay pre-charging protection circuit, so as to solve the above-mentioned technical problems existing in the prior art.

[0009] The objective of the present invention is achieved through the following technical solutions:

[0010] The oscillation suppression method for suppressing a relay pre-charging protection circuit of the present invention introduces a Posicast feedforward controller into a PWM control circuit to suppress and weaken the oscillation.

[0011] Compared with the prior art, the oscillation suppression method for suppressing the relay pre-charging protection circuit provided by the present invention can effectively eliminate the current shock and oscillation caused by relay switching, significantly improve the stability of the pre-charging protection circuit, and can quickly respond to relay switching events and reduce system recovery time, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of a bridgeless PFC topology structure with an EMI filter in the prior art;

[0013] Figure 2 It is a schematic diagram of the output waveform of the power circuit that oscillates when the relay is switched in the prior art;

[0014] Figure 3 This is a schematic diagram of the control circuit framework after the Posicast controller is introduced into the embodiment of the present invention;

[0015] Figure 4 This is a schematic diagram of the output waveform of the power circuit after adding Posicast control in an embodiment of the present invention;

[0016] Figure 5 Schematic diagram of output waveform of power circuit comparison according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0018] The contents not described in detail in the examples of the present invention belong to the prior art known to professionals in the field. If no specific conditions are specified in the examples of the present invention, the conditions are carried out according to the conventional conditions in the field or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used in the examples of the present invention, they are all conventional products that can be purchased commercially.

[0019] The oscillation suppression method for suppressing a relay pre-charging protection circuit of the present invention introduces a Posicast feedforward controller into a PWM control circuit to suppress and weaken the oscillation.

[0020] At the moment of relay switching, the current on the AC side increases instantly. The Posicast feedforward controller divides the input signal into two sub-signals of different amplitudes according to the time interval, sends them to the controlled object, and then superimposes the responses to eliminate the oscillation problem of the system.

[0021] The Posicast feedforward controller represents the step input signal ε(t) as the synthesis of sub-signals ε1(t) and ε2(t), that is:

[0022]

[0023] where t d is the peak time, which indicates the time when the system response reaches the first peak value; σ is the normalized overshoot, which represents the ratio of the system response exceeding the target value.

[0024] The transfer function of the Posicast feedforward controller is:

[0025]

[0026] Then the closed-loop transfer function of the voltage control loop containing the Posicast feedforward controller is, and the transfer function of the PFC pre-charging circuit using a relay in parallel with a resistor is G(s), expressed as:

[0027] G upo (s) = G uo (s)G po (s) / [1+G uo (s)G po (s)]

[0028] Select t based on calculation d =0.17s, and take overshoot σ=0.6.

[0029] In summary, it can be seen that the oscillation suppression method for suppressing the relay pre-charging protection circuit of the embodiment of the present invention can effectively eliminate the current shock and oscillation caused by relay switching, significantly improve the stability of the pre-charging protection circuit, and can quickly respond to relay switching events and reduce system recovery time.

[0030] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the embodiments of the present invention are described in detail with specific embodiments below.

[0031] Example 1

[0032] A new oscillation suppression scheme for suppressing relay pre-charge protection circuit: Introducing Posicast feedforward controller in PWM control circuit to suppress and weaken oscillation, avoid excessive impact current, burn out circuit components, and destroy system operation stability. The specific structure is as follows Figure 3 shown.

[0033] At the moment of relay switching, the current on the AC side increases instantly. Posicast control divides the input signal into two sub-signals with different amplitudes according to the time interval, sends them to the controlled object, and then superimposes the responses to eliminate the oscillation problem of the system. The step input signal ε(t) is expressed as the synthesis of sub-signals ε1(t) and ε2(t), that is,

[0034]

[0035] where t d is the peak time, which indicates the time when the system response reaches the first peak; σ is the normalized overshoot, which represents the ratio of the system response exceeding the target value. The transfer function of the Posicast controller is:

[0036]

[0037] Then the closed-loop transfer function of the voltage control loop containing the Posicast controller is, and the transfer function of the PFC pre-charging circuit using a relay in parallel with a resistor is G(s), expressed as:

[0038] G upo (s) = G uo (s)G po (s) / [1+G uo (s)G po (s)]

[0039] Select t based on calculation d =0.17s, and take overshoot σ=0.6.

[0040] Testing and experimental verification

[0041] The scheme proposed in the present invention is simulated. The natural frequency of the system is set to 50 Hz, and the switching state of the relay is monitored in the simulation. When the relay switching is detected, a switching signal is generated. Then, the Posicast parameters and pulse sequence parameters are calculated, and the correction signal is generated using the parameters.

[0042] u posicast (t)=u(t)+k1u(t-t1)+k2u(t-t2)

[0043] Where u(t) is the input signal after relay switching. The corrected signal is superimposed on the control input of the pre-charging circuit to eliminate the current shock and oscillation caused by relay switching. The output waveform of the power circuit after adding Posicast control is as follows: Figure 4 shown.

[0044] Secondly, compare the output waveform of the power circuit after adding Posicast control. Figure 5 As shown, the effectiveness of the control scheme is verified.

[0045] Experimental results show that the control scheme can effectively eliminate the current shock and oscillation caused by relay switching, significantly improve the stability of the pre-charging protection circuit, and can quickly respond to relay switching events and reduce system recovery time, which has broad application prospects.

[0046] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for suppressing oscillation of a relay pre-charge protection circuit, It is characterized in that A Posicast feedforward controller is introduced into the PWM control circuit to suppress and weaken the oscillation.

2. The method for suppressing oscillation of a relay pre-charging protection circuit according to claim 1, It is characterized in that At the moment of relay switching, the current on the AC side increases instantly. The Posicast feedforward controller divides the input signal into two sub-signals of different amplitudes according to the time interval, sends them to the controlled object, and then superimposes the responses to eliminate the oscillation problem of the system.

3. The oscillation suppression method for suppressing a relay pre-charging protection circuit according to claim 2, It is characterized in that The Posicast feedforward controller represents the step input signal ε(t) as a sub-signal ε 1 (t) and ε 2 (t), namely: where t d is the peak time, which indicates the time when the system response reaches the first peak value; σ is the normalized overshoot, which represents the ratio of the system response exceeding the target value.

4. The method for suppressing oscillation of a relay pre-charging protection circuit according to claim 3, It is characterized in that The transfer function of the Posicast feedforward controller is: Then the closed-loop transfer function of the voltage control loop containing the Posicast feedforward controller is, and the transfer function of the PFC pre-charging circuit using a relay in parallel with a resistor is G(s), expressed as: G upo (s)=G uo (s)G po (s) / [1+G uo (s)G po (s)] Select t based on calculation d =0.17s, and take overshoot σ=0.6.

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