Inverter special waveform control system

Abstract

The invention discloses an inverter special waveform control system which comprises a repetitive control module, and the repetitive control module comprises a repetitive control internal model, an advanced link zm, a gain parameter Kr and a forward low-pass filter S (z) which are connected in sequence. The repetitive control internal model comprises a backward low-pass filter Q (z), a backward delay link z-N and a forward delay link z-N. A high-frequency special waveform is controlled by applying a repetitive control method, and a control system can have very high gains on fundamental waves and infinite-dimensional harmonic waves by introducing an internal model of a periodic signal, so that tracking of the high-frequency special waveform is realized.

Description

Technical Field

[0001] The invention relates to an inverter, and in particular to an inverter special waveform control system. Background Art

[0002] Inverters convert direct current into alternating current and are widely used in civil and industrial fields. Typical inverter circuits are as follows: Figure 1 As shown, the input is a DC voltage, and by controlling the full bridge in a certain way, an AC voltage can be output.

[0003] Existing technology and defects:

[0004] The existing control method is generally a dual PI closed-loop control of the output voltage and inductor current. This control method can only ensure the accuracy of the output low-frequency AC voltage, such as 50Hz AC voltage. If in some special application scenarios, it is hoped to output high-frequency AC voltage, especially special waveforms, such as square waves, triangle waves and other non-sinusoidal waveforms, the traditional dual PI control cannot meet the requirements.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide an inverter special waveform control system to solve the above technical problems existing in the prior art.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] The inverter special waveform control system of the present invention comprises a repetitive control module, wherein the repetitive control module comprises a repetitive control inner model, a leading link z connected in sequence m , gain parameter Kr, forward low-pass filter S(z);

[0009] The repetitive control internal model includes a backward low-pass filter Q(z) and a backward delay link z -N , and a forward delay link z -N .

[0010] Compared with the prior art, the inverter special waveform control system provided by the present invention uses a repetitive control method to control the high-frequency special waveform. By introducing the internal model of the periodic signal, the control system can have a very high gain on the fundamental wave and its infinite-dimensional harmonics, thereby achieving tracking of the high-frequency special waveform. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of an inverter circuit in the prior art.

[0012] Figure 2 4 is a block diagram of a repetition control module according to an embodiment of the present invention.

[0013] Figure 3 This is a comparison chart of the experimental results of the double PI scheme and the repeated control scheme. DETAILED DESCRIPTION

[0014] 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.

[0015] First, the terms that may be used in this article are explained as follows:

[0016] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y means both “X” or “Y” and “X and Y”.

[0017] The terms "include", "comprises", "contains", "has" or other descriptions with similar semantics should be interpreted as non-exclusive inclusion. For example, including certain technical feature elements (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or products, etc.) should be interpreted as including not only certain technical feature elements explicitly listed, but also other technical feature elements known in the art that are not explicitly listed.

[0018] The term "consisting of..." means excluding any technical feature elements not explicitly listed. If this term is used in a claim, it will make the claim closed, so that it does not contain technical feature elements other than the technical feature elements explicitly listed, except for the conventional impurities related to them. If this term only appears in a clause of a claim, it only limits the elements explicitly listed in the clause, and the elements recorded in other clauses are not excluded from the overall claim.

[0019] 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.

[0020] The inverter special waveform control system of the present invention comprises a repetitive control module, wherein the repetitive control module comprises a repetitive control inner model, a leading link z connected in sequence m, gain parameter Kr, forward low-pass filter S(z);

[0021] The repetitive control internal model includes a backward low-pass filter Q(z) and a backward delay link z -N , and a forward delay link z -N .

[0022] The delay link z -N It is the part that constitutes the inner model of the periodic function, the leading link z m The backward low-pass filter Q(z) constitutes a unit for compensating the phase lag of the low-pass filter, the backward low-pass filter Q(z) constitutes a unit for ensuring the stability of the system, the gain parameter Kr constitutes a unit for balancing the stability and response rate of the system, and the forward low-pass filter S(z) constitutes a unit for attenuating the high-frequency noise in the system.

[0023] The delay link z -N Designed to delay one cycle, assuming that the period of the reference signal is T and the discrete step length of the processor is Ts, then N = T / Ts.

[0024] The backward low-pass filter Q(z) is a constant less than 1 or a zero-phase-shift low-pass filter.

[0025] The forward low-pass filter S(z) is a second-order low-pass filter or a Butterworth low-pass filter.

[0026] The leading link z m Select z m *S(z)*Dp(z) has a phase curve close to the zero axis m value in a wider frequency range. By calculating the corresponding phase-frequency response for different m, the best m value is selected.

[0027] The value range of the gain parameter Kr is as follows:

[0028]

[0029] Among them, ω N For z m *S(z)*Dp(z) is the cutoff frequency, θx is the phase of the x link at the ω frequency, and Ax is the amplitude of the x link at the ω frequency.

[0030] In summary, it can be seen that the inverter special waveform control system of the embodiment of the present invention uses a repetitive control method to control the high-frequency special waveform. By introducing the internal model of the periodic signal, the control system can have a very high gain on the fundamental wave and its infinite-dimensional harmonics, thereby achieving tracking of the high-frequency special waveform.

[0031] 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.

[0032] Example 1

[0033] The invention principle description of the present invention:

[0034] Since the typical repetitive control poles are located on the unit circle, it is an unstable system, so it is improved.

[0035] The block diagram of the improved repetitive control module is as follows: Figure 2 As shown, it includes the delay link z -N , advance link z m , backward low-pass filter Q(z), gain parameter Kr, forward low-pass filter S(z). Delay link z -N It is the part that constitutes the inner model of the periodic function, the leading link z m It is used to compensate for the phase lag of low-pass filtering, the backward low-pass filter Q(z) is used to ensure the stability of the system, the gain parameter Kr is used to balance the stability and response rate, and the forward low-pass filter S(z) is used to attenuate the high-frequency noise in the system. Dp(z) is the transfer function of the controlled object.

[0036] Delay link -N design:

[0037] z -N It should be designed to delay by one cycle. Assuming that the period of the reference signal is T and the discrete step length of the processor is Ts, then N = T / Ts.

[0038] Backward low-pass filter Q(z) design:

[0039] Q(z) can be designed as a constant less than 1, such as 0.95, or a zero-phase-shift low-pass filter. Designing it as a constant is simpler and can also reduce the order of the system, but it will produce a certain steady-state error. If the accuracy requirement is high, you can choose to design it as a zero-phase-shift low-pass filter.

[0040] Forward low-pass filter S(z) design:

[0041] S(z) can be designed as a second-order low-pass filter or a Butterworth low-pass filter.

[0042] Advanced Link m design:

[0043] Because z m To compensate for phase lag, we should choose m *S(z)*Dp(z) has a phase curve close to the zero axis m value in a wider frequency range. The best m value can be selected by calculating the corresponding phase-frequency response for different m.

[0044] Gain parameter Kr:

[0045] The value range of Kr is as follows:

[0046]

[0047] Among them, ω N For z m *S(z)*Dp(z) is the cutoff frequency, θx is the phase of the x link at the ω frequency, and Ax is the amplitude of the x link at the ω frequency.

[0048] The larger the Kr is, the closer the Nyquist curve is to the center, the higher the system stability is, but the slower the adjustment speed is. Therefore, the selection of Kr should ensure that the system has a certain stability margin while having a faster adjustment speed.

[0049] Testing and experimental verification:

[0050] The scheme proposed in the present invention is compared with the traditional dual PI scheme through simulation experiments. The output is set to 100V 1000Hz triangle wave and square wave, and the experiments are carried out under no load and 10Ω load respectively. The experimental results are shown in the figure. Figure 3 As shown, the red curve is the reference voltage and the green curve is the controller output.

[0051] from Figure 3 It can be seen from the results that the dual PI scheme has a large error in controlling the 1000Hz triangle wave and square wave, especially when the load is heavier, while the repetitive control scheme has a better control effect. Whether in no-load or loaded conditions, the control error is small, which verifies that the repetitive control method is suitable for controlling high-frequency special waveforms.

[0052] 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. An inverter special waveform control system, characterized in that: The repetitive control module includes a repetitive control inner model, a leading link z connected in sequence. m , gain parameter Kr, forward low-pass filter S(z); The repetitive control internal model includes a backward low-pass filter Q(z) and a backward delay link z -N , and a forward delay link z -N .

2. The inverter special waveform control system according to claim 1, characterized in that: The delay link z -N It is the part that constitutes the inner model of the periodic function, the leading link z m The backward low-pass filter Q(z) constitutes a unit for compensating the phase lag of the low-pass filter, the backward low-pass filter Q(z) constitutes a unit for ensuring the stability of the system, the gain parameter Kr constitutes a unit for balancing the stability and response rate of the system, and the forward low-pass filter S(z) constitutes a unit for attenuating the high-frequency noise in the system.

3. The inverter special waveform control system according to claim 1 or 2, characterized in that: The delay link z -N Designed to delay one cycle, assuming that the period of the reference signal is T and the discrete step length of the processor is Ts, then N = T / Ts.

4. The inverter special waveform control system according to claim 1 or 2, characterized in that: The backward low-pass filter Q(z) is a constant less than 1 or a zero-phase-shift low-pass filter.

5. The inverter special waveform control system according to claim 1 or 2, characterized in that: The forward low-pass filter S(z) is a second-order low-pass filter or a Butterworth low-pass filter.

6. The inverter special waveform control system according to claim 1 or 2, characterized in that: The leading link z m Select z m *S(z)*Dp(z) has a phase curve close to the zero axis m value in a wider frequency range. By calculating the corresponding phase-frequency response for different m, the best m value is selected.

7. The inverter special waveform control system according to claim 1 or 2, characterized in that: The value range of the gain parameter Kr is as follows: Among them, ω N For z m *S(z)*Dp(z) is the cutoff frequency, θx is the phase of the x link at the ω frequency, and Ax is the amplitude of the x link at the ω frequency.

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