A method for suppressing double power frequency fluctuation based on current feedforward

Abstract

The application relates to a double-frequency fluctuation suppression method based on current feedforward, which is applied to a DC-DC converter and comprises the following steps: S1, collecting output voltage V of a single-phase uncontrolled rectification bridge after-stage DC-DC converter o and inductor current I L ; S2, respectively calculating a first PI output value and a feedforward value based on the output voltage V o and the inductor current I L , and taking a difference value of the first PI output value and the feedforward value as a second PI output value; and S3, calculating a duty cycle of a switching tube according to the second PI output value to suppress double-frequency fluctuation. The application improves input transient response speed of the DC-DC converter and enhances anti-interference capability of the DC-DC converter; reduces difficulty of PI design of a control loop; greatly reduces influence of double-frequency fluctuation of the single-phase uncontrolled rectification on the after-stage DC-DC converter; and does not need to increase any external device, is suitable for wide application, and is simple to control.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronic applications, and particularly relates to a double-frequency fluctuation suppression method based on current feedforward. BACKGROUND

[0002] With the rapid development of science and technology, the update speed of electronic products becomes faster and faster. Most of the electronic products are powered by DC power supplies, and the rapid development of the electronic products also puts forward more stringent requirements for the DC power supplies. The DC voltage of the electronic products is usually obtained by passing the mains through an uncontrolled rectifier bridge and then through a DC-DC converter. For any application with a load, whether it is a mobile phone, a tablet computer, a wearable device or a car electronics, without stable power supply, it cannot work normally.

[0003] In actual engineering applications, the front-end input of the DC-DC converter is usually obtained by passing the mains through an uncontrolled rectifier bridge. Single-phase uncontrolled rectification often leads to double-frequency fluctuation of the input voltage of the rear-stage DC-DC converter about the fundamental wave of the grid voltage. The traditional PI control method works under this condition. Since the transient response speed of the PI control method is slow, the output current is easily affected by the fluctuation, which leads to the output current being easily shaken or the phenomenon, which greatly reduces the quality of the output current or voltage and greatly reduces the service life of the device.

[0004] Therefore, it is necessary to provide a new double-frequency fluctuation suppression method based on current feedforward to solve the above technical problems. SUMMARY

[0005] The purpose of the application is to provide a double-frequency fluctuation suppression method based on current feedforward to solve the above problems.

[0006] The application achieves the above purpose by the following technical solutions:

[0007] A double-frequency fluctuation suppression method based on current feedforward, the method is applied to a DC-DC converter, and includes the following steps:

[0008] S1: collecting the output voltage V of the single-phase uncontrolled rectifier bridge rear-stage DC-DC converter o and the inductor current I L ;

[0009] S2: calculating a first PI output value and a feedforward value based on the output voltage V o and the inductor current I L respectively, and taking the difference between the first PI output value and the feedforward value as a second PI output value;

[0010] S3: calculating the duty cycle of the switching tube according to the second PI output value to suppress the double-frequency fluctuation.

[0011] As a further optimization scheme of the present application, in the step S2, based on the output voltage V o and the inductor current I L , a first PI output value and a feedforward value are respectively calculated, and a difference between the first PI output value and the feedforward value is taken as a second PI output value.

[0012] The calculation formula of the first PI output value is as follows:

[0013] V PI = K P (V REF -V o ) + K I ∑(V REF -V o ).

[0014] In the formula, V REF is a reference voltage, K P is a proportional coefficient, and K I is an integral coefficient.

[0015] The calculation formula of the feedforward value is as follows:

[0016]

[0017] In the formula, K is a feedforward coefficient.

[0018] The calculation formula of the second PI output value is as follows:

[0019]

[0020] As a further optimization scheme of the present application, the reference voltage V REF = 500 V, the proportional coefficient K P = 94, the integral coefficient K I = 0.005, and the feedforward coefficient K = 2.

[0021] As a further optimization scheme of the present application, in the step S3, according to the second PI output value, the calculation formula of the duty cycle of the switching tube is as follows:

[0022] D = K d V′ PI .

[0023] In the formula, K d is a conversion coefficient of the PI output value and the duty cycle.

[0024] As a further optimization scheme of the present application, the conversion coefficient K d = 0.00005.

[0025] The application has the advantages that:

[0026] 1. The application improves the input transient response speed of the DC-DC converter and enhances the anti-interference ability thereof;

[0027] 2. The application reduces the difficulty of PI design of the control loop and greatly reduces the influence of the double power frequency fluctuation existing in the single-phase uncontrolled rectification on the DC-DC converter in the rear stage;

[0028] 3. The application does not need to increase any external device, has strong applicability, simple control and easy realization. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a flow chart of the control method of the application;

[0030] Figure 2 is a complete main circuit diagram of the Boost converter of the embodiment;

[0031] Figure 3 is an input waveform diagram of the Boost converter;

[0032] Figure 4 is an output voltage waveform when the PI parameter is small in the traditional PI control method;

[0033] Figure 5 is an inductance current waveform when the PI parameter is small in the traditional PI control method;

[0034] Figure 6 is an output voltage waveform when the PI parameter is large in the traditional PI control method;

[0035] Figure 7 is an inductance current waveform when the PI parameter is large in the traditional PI control method;

[0036] Figure 8 is an output voltage waveform of the current feedforward PI control method;

[0037] Figure 9 is an inductance current waveform of the current feedforward PI control method. DETAILED DESCRIPTION

[0038] The application will be described in further detail below with reference to the drawings. It is necessary to point out here that the following detailed description is only used to further illustrate the application and cannot be understood as limiting the protection scope of the application. Those skilled in the art can make some non-essential improvements and adjustments to the application according to the above application content.

[0039] Embodiment 1

[0040] As DC-DC converter has multiple topologies, the embodiment takes Boost converter as an example.

[0041] As shown in the figure, a method for suppressing double frequency fluctuation based on current feedforward for Boost converter, comprising the following steps: Figures 1-9

[0042] Table 1. Parameters of Boost converter in the embodiment of the application

[0043]

[0044] S1: Collect the output voltage and inductance current of the Boost converter, wherein the sampling value of the output voltage is V o , and the sampling value of the inductance current is I L .

[0045] S2: Calculate the first PI output value according to the sampling value of the output voltage, and the calculation formula of the first PI output value is:

[0046] V PI =K P (V REF -V o )+K I ∑(V REF -V o );

[0047] In this example, V REF = 500V, K P = 94, and K I = 0.005.

[0048] S3: Calculate the feedforward current value according to the sampling value of the inductance current, and the calculation formula is:

[0049]

[0050] In this example, K = 2.

[0051] S4: Subtract the feedforward current from the PI output to obtain the second PI output value, and then:

[0052]

[0053] S5: Calculate the duty cycle of the switch tube according to the second PI output value, and the calculation method of the duty cycle is:

[0054] D=K d V′ PI ;

[0055] In this example, K d = 0.00005. ​

[0056] Figure 3 The waveform of the input voltage is shown. Figure 4 and Figure 5 The output voltage and inductor current waveforms of the traditional PI control method when the PI parameters are small are shown. Figure 6 and Figure 7 The output voltage and inductor current waveforms of the traditional PI control method when the PI parameters are large are shown. Figure 8 and Figure 9 The output voltage and inductor current waveforms of the current feedforward PI control method are shown. Figure 3 It can be seen from the figure that the input voltage has a double frequency fluctuation. Figures 4-7 It can be seen from the figure that when the input voltage has a double frequency fluctuation, the system response is slow when the PI parameters are small, and the inductor current is discontinuous; the system response is too fast when the PI parameters are large, and the inductor current is high-frequency oscillation. Figures 4-7 Figures 8-9 It can be seen from the figures that the control method of the application effectively suppresses the inductor current discontinuity and oscillation caused by the double frequency fluctuation while ensuring fast system response.

[0057] The above-described embodiments only express several embodiments of the application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent of the application. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are all within the protection scope of the application.​

Claims

1. A current feedforward-based double line frequency fluctuation suppression method, the method being applied to a DC-DC converter, characterized in that, The method comprises the following steps: S1: Collecting output voltage of single-phase uncontrolled rectifier bridge post-stage DC-DC converter V o and inductor current I L ; S2: calculating a first PI output value and a feedforward value based on the output voltage V o and the inductor current I L respectively calculating a first PI output value and a feedforward value, and taking a difference between the first PI output value and the feedforward value as a second PI output value S3: calculating the duty cycle of the switch tube according to the second PI output value to suppress the double power frequency fluctuation; In the step S2, the output voltage V o and the inductor current I L The step of calculating the first PI output value and the feedforward value respectively, and taking the difference between the first PI output value and the feedforward value as the second PI output value is specifically: The calculation formula of the first PI output value is as follows: ; wherein V REF is a reference voltage, K P is a proportional coefficient, K I is an integral coefficient; The calculation formula of the feedforward value is as follows: ; In the formula, K is a feedforward coefficient; The calculation formula of the second PI output value is as follows: ; In the step S3, the duty cycle of the switch tube is calculated according to the second PI output value, and the calculation formula is as follows: ; In the formula, Kd is the conversion coefficient of the PI output value and the duty cycle.

2. The method according to claim 1, wherein the method is characterized by: the reference voltage V REF = 500 V, the proportional coefficient K P = 94, the integral coefficient K I = 0.005, the feedforward coefficient K = 2.

3. The method of claim 1, wherein the method is characterized by: The conversion coefficients K d = 0.00005.

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