Single-phase converter and control method thereof

Abstract

The invention provides a single-phase current converter and a control method thereof, the single-phase current converter comprises a switch unit, and the switch unit comprises a first bridge arm and a second bridge arm which are connected in parallel; the method comprises the following steps: determining a reference alternating current is * based on an alternating voltage vs of an alternating current side of the single-phase converter and a reference direct current voltage vdc * of a direct current side of the single-phase converter; determining the waveform of a modulation wave based on the reference alternating current is *, the actual alternating current is, the direct current voltage vdc of the direct current side, the reference direct current voltage vdc * and the alternating current voltage vs; performing modulation based on the waveform of the modulation wave to obtain a control signal of the switch unit; and controlling the first bridge arm and the second bridge arm based on the control signal.

Description

Technical Field

[0001] The present disclosure relates to the field of electric power technology, and in particular to a single-phase converter and a control method thereof. Background Art

[0002] Single-phase converters are used in small power conversion scenarios, such as photovoltaic power grid connection, uninterruptible power supply, electric vehicle charging, etc. Traditional control methods for single-phase converters are mostly based on linear systems, while single-phase converters are nonlinear systems, especially in the face of large signal disturbances, it is difficult to achieve a good control effect and has certain limitations. Summary of the invention

[0003] In view of this, the purpose of the present disclosure is to provide a single-phase converter and a control method thereof to solve technical problems such as poor control effect of the single-phase converter.

[0004] Based on the above purpose, in a first aspect, the present disclosure provides a control method for a single-phase converter, wherein the single-phase converter includes a switch unit, and the switch unit includes a first bridge arm and a second bridge arm connected in parallel;

[0005] Methods include:

[0006] Based on the AC voltage v on the AC side of the single-phase converter s and the reference DC voltage v on the DC side dc *Determine the reference AC current i s *;

[0007] Based on the reference AC current i s *、Actual AC current i s , DC voltage v on the DC side dc , reference DC voltage v dc * and AC voltage v s Determine the waveform of the modulating wave;

[0008] Modulating based on the waveform of the modulation wave to obtain a control signal of the switch unit;

[0009] The first bridge arm and the second bridge arm are controlled based on the control signal.

[0010] In another aspect, the present disclosure provides a single-phase converter controlled by the method according to the first aspect.

[0011] It can be seen from the above that the single-phase converter and control method thereof provided by the present disclosure, based on the hybrid potential function theory and the power shaping control (PSC) method based on the BM model, can significantly improve the dynamic response characteristics of the single-phase converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the present disclosure or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0013] Figure 1 Schematic main circuit diagram of a single-phase inverter according to an embodiment of the present disclosure.

[0014] Figure 2 It is a schematic principle diagram of a control method for a single-phase converter according to an embodiment of the present disclosure.

[0015] Figure 3 Schematic diagram of DC voltage waveforms under different control schemes when the load power changes according to an embodiment of the present disclosure.

[0016] Figure 4 Schematic diagram of DC voltage waveforms under different control schemes during load startup according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0017] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0018] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the embodiments of the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0019] Single-phase converters are used in small power conversion scenarios, such as photovoltaic power grid connection, uninterruptible power supply, electric vehicle charging, etc. Traditional control methods are mostly based on linear systems, while single-phase converters are nonlinear systems. Especially in the face of large signal disturbances, traditional control methods often cannot respond quickly, resulting in unstable output or reduced control performance, making it difficult to achieve better control accuracy and effect, and having certain limitations. Therefore, how to improve the control accuracy of single-phase converters is a technical problem that needs to be solved urgently.

[0020] In view of this, the embodiments of the present disclosure provide a single-phase converter and a control method thereof, based on the hybrid potential function theory and a power shaping control (PSC) method based on the BM model, which can significantly improve the dynamic response characteristics of the single-phase converter.

[0021] See also Figure 1 , Figure 1 A schematic main circuit diagram of a single-phase inverter according to an embodiment of the present disclosure is shown. Figure 1 In the embodiment, the single-phase converter 100 includes a first filter unit 110, a switch unit 120 and a second filter unit 130 connected in sequence. Specifically, the first side of the first filter unit 110 can be connected to an AC power source, and the voltage of the AC power source can be an AC voltage v s The second side of the first filter unit 110 is connected to the AC side of the switch unit 120, the DC side of the switch unit 120 is connected to the first side of the second filter unit 130, and the second side of the second filter unit 130 is connected to the load P CPL Connection, load P CPL The voltage across the two ends is a DC voltage v dc .

[0022] In some embodiments, the first filtering unit 110 may include an equivalent resistor r and an inductor L connected in series. s Specifically, Figure 1 As shown, the first end of the equivalent resistor r is connected to the first end of the AC power supply, and the second end of the equivalent resistor r is connected to the inductor L s The first end of the link, inductor L s The second end of is connected to the switch unit 120. s The current is the AC inductor current i s .

[0023] In some embodiments, the switch unit 120 may include a first bridge arm and a second bridge arm connected in parallel. Further, the first bridge arm may include a first switch S1 and a second switch S2 connected in series, and the second bridge arm may include a third switch S3 and a fourth switch S4 connected in series. Figure 1 As shown, the first end of the first switch S1 is connected to the first end of the third switch S3, the second end of the first switch S1 and the first end of the second switch S2 are connected to the first midpoint a, and the inductor L s The second end of the AC power source is also connected to the first midpoint a. The second end of the third switch S3 and the first end of the fourth switch S4 are connected to the second midpoint b, and the second end of the second switch S2 and the second end of the fourth switch S4 are connected. The second end of the AC power source is connected to the second midpoint b, and the voltage between the first midpoint a and the second midpoint b is v ab .

[0024] Further, in some embodiments, two ends of the first switch S1 , the second switch S2 , the third switch S3 , and the fourth switch S4 may have parallel diodes.

[0025] In some embodiments, the second filtering unit 130 may include a capacitor C dc Specifically, the capacitor C dc The first end of the capacitor C is connected to the connection point of the first switch S1 and the third switch S3. dc The second end of the capacitor C is connected to the connection point of the second switch S2 and the fourth switch S2. Further, in some embodiments, the capacitor C dc The second end of can be grounded. Figure 1 As shown, the load P CPL Connected in parallel at both ends of the second filter unit 130, the load P CPL The voltage across the capacitor C dc The voltage at both ends is a DC voltage v dc .

[0026] See also Figure 2 , Figure 2 A schematic diagram of a control method for a single-phase converter according to an embodiment of the present disclosure is shown. Figure 1 and Figure 2 , a control method for a single-phase converter may include:

[0027] Based on the AC voltage v on the AC side of the single-phase converter s and the reference DC voltage v on the DC side dc *Determine the reference AC current i s *;

[0028] Based on the reference AC current i s *、Actual AC current i s , DC voltage v on the DC side dc , reference DC voltage v dc * and AC voltage v s Determine the waveform of the modulating wave;

[0029] Performing modulation based on the waveform of the modulation wave to obtain a control signal of the switch unit;

[0030] The switch unit of the unidirectional converter is controlled based on the control signal.

[0031] Among them, the AC voltage v on the AC side can be obtained s , actual AC current i s and the DC voltage v on the DC side dc For example, a voltage sensor can be used to detect the AC voltage v s and the DC voltage v on the DC side dc, using current sensor to detect actual AC current i s Based on the AC voltage v on the AC side of the single-phase converter s and the reference DC voltage v on the DC side of the single-phase converter dc *, first determine the reference AC current i s *. Then, based on the reference AC current i s *、Actual AC current i s , DC voltage v on the DC side dc , reference DC voltage v dc * and AC voltage v s , determine the waveform of the modulation wave. Then, modulate based on the waveform of the modulation wave to obtain the control signal of the switch unit. Finally, control the switch unit of the single-phase converter based on these control signals to achieve precise control of the single-phase converter.

[0032] In some embodiments, based on the AC voltage v on the AC side of the single-phase inverter s and the reference DC voltage v on the DC side of the single-phase converter dc *Determine the reference AC current I s *,include:

[0033] Among them, V s is the AC voltage v s The maximum value of the equivalent resistance of the AC side equivalent resistance, R L is the load resistance value of the DC side load.

[0034] Specifically, the AC voltage v on the AC side s Can be v s =V s sinωt, in order to achieve unity power factor, the current is in phase with the system voltage, and a second-order generalized integrator (SOGI) phase lock is used. The AC reference current on the flow side can be expressed as:

[0035] i s * =I s * sinωt (1)

[0036] Where Is* is the reference value of the maximum current, which can be expressed as:

[0037]

[0038] In the formula, Vs is the maximum value of the AC voltage vs, r is the equivalent resistance value on the AC side, R L is the equivalent resistance value of the DC side, i.e. the resistance value of the load, v dc *Reference value of DC voltage.

[0039] In some embodiments, based on the reference AC current i s *、Actual AC current i s , DC voltage v on the DC side dc , reference DC voltage v dc * and AC voltage v s Determine the waveform of the modulated wave, including:

[0040]

[0041] Among them, μ is the modulation wave, R1 is the virtual series dissipative damping coefficient, R2 is the virtual parallel dissipative damping coefficient, L s is the inductance value of the AC side inductor, is the derivative of the reference DC voltage, is the derivative of the reference AC current. The constraint limit of the damping injection coefficient is:

[0042]

[0043] Where δ is a tuning parameter, and 0<δ<1. max|μ| is the maximum amplitude of the modulation wave, that is, the maximum amplitude of the switching function Sab.

[0044] In some embodiments, performing modulation based on the waveform of the modulation wave to obtain a control signal of the switch unit includes:

[0045] modulating the modulated wave based on a triangular carrier wave, and determining that the control signal of the first bridge arm at time t is a first signal when the amplitude of the modulated wave at time t is greater than or equal to the amplitude of the triangular carrier wave;

[0046] When the amplitude of the modulated wave at time t is less than the amplitude of the triangular carrier, determining that the control signal of the first bridge arm at time t is the second signal;

[0047] A third signal of the second bridge arm is determined based on the first signal or the second signal.

[0048] Specifically, Figure 2 As shown in the figure, when a two-level single-phase converter is used and bipolar SPWM modulation is used, μ is the modulation wave and vz is the triangular carrier. When μ>vz, Sa is 1, otherwise it is 0. The modulation method of phase b is the same as that of phase a, except that the phase difference between the modulation waves of phase a and phase b is 180°, where Sa and Sb are the switching functions of the first bridge arm and the second bridge arm respectively.

[0049] See also Figure 3 , Figure 3The waveform diagram of the DC voltage under different control schemes when the load power changes according to the embodiment of the present disclosure is shown. It can be seen that when the load power suddenly changes from 2kW to 3kW, compared with the traditional PI control, the control method (PSC) proposed in the embodiment of the present disclosure has a faster response time and a smaller voltage drop amplitude, and the control effect is equivalent to the passive control (PBC). Figure 4 , Figure 4 The waveform diagram of the DC voltage under different control schemes during load startup according to the embodiment of the present disclosure is shown. Compared with the traditional PI control, the voltage overshoot of the control method (PSC) proposed in the embodiment of the present disclosure is reduced from 100V to 0V, and the startup time is reduced from 0.2s to 0.15s. Compared with the PBC control, the voltage overshoot of the PSC is reduced from 30V to 0V, and there is no voltage drop phenomenon.

[0050] It can be seen that the control method of the embodiment of the present disclosure, based on the mixed potential function theory and the power shaping control (Power Shaping Controller, PSC) method based on the BM model, can significantly improve the dynamic response characteristics of the single-phase converter. The scheme of the embodiment of the present disclosure can improve the control accuracy of the single-phase converter, and by quickly adjusting the control signal, the response speed of the single-phase converter to load changes and power grid disturbances can be improved, thereby improving the dynamic performance of the system, reducing the occurrence of abnormal conditions such as overvoltage and overcurrent, and improving the reliability and stability of the system. Thereby reducing switching losses and improving the overall efficiency of the converter. In addition, the design of the control system is simplified and the implementation complexity is reduced. Efficient energy conversion is achieved, and the overall performance and reliability of the system are improved.

[0051] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples. Based on the concept of the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present disclosure as described above, which are not provided in detail for the sake of simplicity.

[0052] In addition, to simplify the description and discussion, and in order not to make the embodiments of the present disclosure difficult to understand, the known power / ground connections to the integrated circuit (IC) chips and other components may or may not be shown in the provided figures. In addition, the device can be shown in the form of a block diagram to avoid making the embodiments of the present disclosure difficult to understand, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform on which the embodiments of the present disclosure will be implemented (that is, these details should be fully within the scope of understanding of those skilled in the art). Where specific details (e.g., circuits) are set forth to describe exemplary embodiments of the present disclosure, it is apparent to those skilled in the art that the embodiments of the present disclosure can be implemented without these specific details or with changes in these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0053] The embodiments of the present disclosure are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A control method for a single-phase converter, characterized in that: The single-phase converter comprises a switch unit, and the switch unit comprises a first bridge arm and a second bridge arm connected in parallel; Methods include: Based on the AC voltage v on the AC side of the single-phase converter s and the reference DC voltage v on the DC side dc *Determine the reference AC current i s *; Based on the reference AC current i s *、Actual AC current i s , DC voltage v on the DC side dc , reference DC voltage v dc * and AC voltage v s Determine the waveform of the modulating wave; Modulating based on the waveform of the modulation wave to obtain a control signal of the switch unit; The first bridge arm and the second bridge arm are controlled based on the control signal.

2. The method according to claim 1, characterized in that Based on the AC voltage v on the AC side of the single-phase converter s and the reference DC voltage v on the DC side of the single-phase converter dc *Determine the reference AC current I s *,include: Among them, V s is the AC voltage v s The maximum value of the equivalent resistance of the AC side equivalent resistance, R L is the load resistance value of the DC side load.

3. The method according to claim 2, characterized in that Based on the reference AC current i s *、Actual AC current i s , DC voltage v on the DC side dc , reference DC voltage v dc * and AC voltage v s Determine the waveform of the modulated wave, including: Among them, μ is the modulation wave, R1 is the virtual series dissipative damping coefficient, R2 is the virtual parallel dissipative damping coefficient, L s is the inductance value of the AC side inductor, is the derivative of the reference DC voltage, is the derivative of the reference AC current.

4. The method according to claim 3, characterized in that: The constraints of the virtual series dissipative damping coefficient and the virtual parallel dissipative damping coefficient include: δ is a tuning parameter with 0<δ<1, and max|μ| is the maximum amplitude of the modulated wave.

5. The method according to claim 4, characterized in that Modulation based on the waveform of the modulating wave, including: Modulating the modulation wave based on the triangular carrier wave, when the amplitude of the modulation wave at time t is greater than or equal to the amplitude of the triangular carrier wave, determining that the control signal of the first bridge arm at time t is the first signal; When the amplitude of the modulated wave at time t is less than the amplitude of the triangular carrier, determining that the control signal of the first bridge arm at time t is the second signal; The third signal of the second bridge arm is determined based on the first signal or the second signal.

6. The method according to claim 5, characterized in that The modulation includes bipolar SPWM modulation.

7. The method according to claim 6, characterized in that The phase difference between the control signal of the first bridge arm and the control signal of the second bridge arm is 180°.

8. A single-phase converter, characterized in that: The control is performed using a method according to any one of claims 1 to 7.

9. The single-phase converter according to claim 8, characterized in that: The single-phase converter also includes a first filter unit and a second filter unit. The first filter unit, the switch unit and the second filter unit are connected in sequence. The input side of the first filter unit is connected to the AC power supply, and the output side of the second filter unit is connected to the load.

10. The single-phase converter according to claim 9, characterized in that: The first filtering unit includes an equivalent resistor and an inductor connected in series; a first end of the equivalent resistor is connected to a first end of the AC power supply, a second end of the equivalent resistor is linked to a first end of the inductor, and a second end of the inductor is connected to the switch unit; The switch unit includes a first bridge arm and a second bridge arm connected in parallel; the first bridge arm includes a first switch S1 and a second switch S2 connected in series, and the second bridge arm includes a third switch S3 and a fourth switch S4 connected in series; the first end of the first switch S1 is connected to the first end of the third switch S3, and the second end of the first switch S1 and the first end of the second switch S2 are connected to the first midpoint a, and the inductor L s The second end of the third switch S3 and the first end of the fourth switch S4 are connected to the second midpoint b, and the second end of the second switch S2 and the second end of the fourth switch S4 are connected; the second end of the AC power supply is connected to the second midpoint b; The second filtering unit includes a capacitor, a capacitor C dc The first end of the capacitor C is connected to the connection point of the first switch S1 and the third switch S3. dc The second end of is connected to the connection point of the second switch S2 and the fourth switch S2, and the load is connected in parallel at both ends of the second filtering unit.

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