A secondary ripple suppression circuit and control method for energy storage system

Abstract

The present invention discloses a secondary ripple suppression circuit and control method for energy storage system, which relates to the technical field of power electronic converter. The circuit includes a filter capacitor C 1 、Filter capacitor C 2 、Filter capacitor C 3 , DC bus support capacitor C d c , power switch tube S 1 , power switch tube S 2 , filter inductor L A , energy storage power supply Us, grid-connected inverter and control circuit, and obtain the filter capacitor C 3 The voltage reference value is then compared with the filter capacitor C 3 The voltage of the switch tube S is subtracted and then input into the controller, and then the PWM modulator is used to obtain the switching tube S 1 , S 2 The secondary ripple suppression circuit provided by the present invention replaces the traditional LC passive filter, realizes the complete absorption of the secondary ripple, greatly reduces the volume of the filter device required in the circuit, and improves the power density of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic converters, and in particular to a secondary ripple suppression circuit and a control method applied to an energy storage system. Background Art

[0002] With the rapid development and popularity of renewable energy sources, such as wind and solar, the power system is facing increasing challenges and opportunities. The unpredictability and intermittency of these renewable energy sources have brought new challenges to the stability of the power grid. In order to overcome these problems and promote the large-scale integration of renewable energy, energy storage systems have been widely studied and applied.

[0003] Energy storage systems can effectively balance power fluctuations and energy demand on the power grid by storing electrical energy in batteries or other devices and releasing it when needed. However, energy storage systems often face the problem of secondary ripple on the DC side during storage and release, which is mainly generated by the energy storage inverter, affecting the voltage quality of the DC bus and reducing the efficiency, stability and life of the energy storage power supply. When the input source is a fuel cell, the secondary ripple current will increase the maximum instantaneous output power of the fuel cell, increase the capacity of the required fuel cell, and thus increase the system cost. In order to solve the secondary ripple problem in the energy storage inverter, a variety of suppression technologies have been proposed, including the use of passive filters, control strategy optimization, and hardware design improvements. Traditional LC passive filters can usually effectively filter out ripples, but increase system cost and volume, and may introduce new losses and failure risks. Control strategy optimization adjusts the operating mode and frequency of the switching device to minimize the generation and propagation of secondary ripples in the DC bus, achieving low cost and suitable for upgrading existing circuits, but it will significantly transfer the pulsating power to the power supply, resulting in a reduced power supply life. Therefore, it is particularly important to design an effective secondary ripple suppression circuit and its control method, which can not only improve the overall efficiency and stability of the energy storage system, but also reduce the cost and maintenance requirements of the system, and promote the widespread application of energy storage technology in power systems. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the problems existing in the above-mentioned existing secondary ripple suppression circuit and control method applied to energy storage systems, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to provide a secondary ripple suppression circuit and control method for energy storage systems, which aims to overcome the shortcomings and deficiencies of the above-mentioned prior art and provide a secondary ripple suppression circuit and control method for energy storage systems, which can use fewer switching devices, and the voltage control is achieved by connecting an integrator and a bandpass filter in parallel, thereby ensuring DC voltage regulation and secondary ripple suppression respectively.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A secondary ripple suppression circuit for an energy storage system, comprising: a filter capacitor C1, a filter capacitor C2, a filter capacitor C3, a DC bus support capacitor C dc , power switch tube S1, power switch tube S2, filter inductor L A , Energy storage power supply U s , grid-connected inverter and control circuit;

[0009] One end of the filter capacitor C1 is connected to the energy storage power supply U s The positive pole of the DC bus support capacitor C dc One end is connected to the positive pole of the grid-connected inverter input terminal, and the other end is connected to the filter inductor L A One end of the filter capacitor C3; filter inductor L A The other end of the filter inductor C2 is connected to the collector of the power switch tube S1 and the emitter of the power switch tube S2; one end of the filter inductor C2 is connected to the collector of the power switch tube S1, and the other end is connected to the emitter of the power switch tube S2, the other end of the filter capacitor C3, and the energy storage power supply U s The negative pole of the DC bus support capacitor C dc The other end of the grid-connected inverter is connected to the negative pole of the input terminal.

[0010] As a preferred solution of the secondary ripple suppression circuit applied to the energy storage system described in the present invention, the switch tube S1 and the switch tube S2 are both switch tubes with anti-parallel diodes.

[0011] The control method of the secondary ripple suppression circuit applied to the energy storage system includes the following steps:

[0012] Step S01, subtracting the voltage reference value of the filter capacitor C2 from the voltage of the filter capacitor C2 to obtain a voltage deviation value of the filter capacitor C2;

[0013] Step S02, inputting the voltage deviation value of the filter capacitor C2 into the controller G1(s), and multiplying the output of the controller G1(s) by the voltage differential value of the filter capacitor C1;

[0014] Step S03, adding the result of the multiplication in step S02, the DC component reference value of the voltage of the filter capacitor C3 and the secondary ripple component reference value of the voltage of the filter capacitor C3 to obtain a voltage reference value of the filter capacitor C3;

[0015] Step S04, subtracting the voltage reference value of the filter capacitor C3 from the voltage of the filter capacitor C3 to obtain a voltage deviation value of the filter capacitor C3;

[0016] Step S05, inputting the voltage deviation value of the filter capacitor C3 into the controller G2(s), and then obtaining the modulation signals of the switch tube S1 and the switch tube S2 through the PWM modulator.

[0017] As a preferred solution of a control method for a secondary ripple suppression circuit applied to an energy storage system described in the present invention, the voltage u1 across the filter capacitor C1, the voltage u2 across the filter capacitor C2, and the voltage u3 across the filter capacitor C3 are regulated by controlling the on and off of the switch tube S1 and the switch tube S2 to suppress the secondary ripple on the DC side.

[0018] As a preferred solution of the control method of the secondary ripple suppression circuit applied to the energy storage system described in the present invention, the controller G1(s) in step S02 is a PI controller, and its transfer function is:

[0019]

[0020] Among them, K 1p and K 1i are the PI parameters of the controller respectively.

[0021] As a preferred solution of the control method of a secondary ripple suppression circuit applied to an energy storage system described in the present invention, wherein: the secondary ripple voltage reference value of the filter capacitor C3 in step S03 is the voltage of the filter capacitor C1 filtered and inverted by a bandpass filter with twice the output frequency.

[0022] As a preferred solution of the control method of the secondary ripple suppression circuit applied to the energy storage system described in the present invention, the controller G2(s) in step S05 is a parallel connection of an integrator and a bandpass filter, and its transfer function is:

[0023]

[0024] Among them, K 2i is the adjustment coefficient of the integrator, ξ is the equivalent quality factor of the bandpass filter, and ω is the AC output frequency of the inverter.

[0025] Beneficial effects of the present invention:

[0026] 1. The secondary ripple suppression circuit and control method provided by the present invention can achieve complete absorption of the secondary ripple, greatly reduce the volume of the filter components required in the circuit, and improve the power density of the system;

[0027] 2. The present invention does not need to change the original inverter structure, and can work by simply connecting in parallel on the DC side of the inverter, realizing hot-swappable operation, and has no effect on the AC side of the inverter. The secondary ripple power is only transmitted between the AC side of the inverter and the branch, thereby improving the service life of the power supply and the operating stability of the system;

[0028] 3. The secondary ripple suppression circuit provided by the present invention requires fewer components, only 2 power switch tubes, 3 capacitors and 1 inductor, with simple control and low loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0030] Figure 1 This is a structural diagram of a secondary ripple suppression circuit disclosed in an embodiment of the present invention.

[0031] Figure 2 It is a schematic diagram of a closed-loop control scheme of a secondary ripple suppression circuit disclosed in an embodiment of the present invention.

[0032] Figure 3 This is a flow chart of the control method disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0036] Reference Figure 1-2 , is an embodiment of the present invention, and provides a secondary ripple suppression circuit for energy storage system, the circuit comprising: filter capacitor C1, filter capacitor C2, filter capacitor C3, DC bus support capacitor C dc , power switch tube S1, power switch tube S2, filter inductor L A , Energy storage power supply U s , a grid-connected inverter and a control circuit; the switch tube S1 and the switch tube S2 are both switch tubes with anti-parallel diodes.

[0037] One end of the filter capacitor C1 is connected to the energy storage power supply U s The positive pole of the DC bus support capacitor C dc One end is connected to the positive pole of the grid-connected inverter input terminal, and the other end is connected to the filter inductor L A One end of the filter capacitor C3; filter inductor L A The other end of the filter inductor C2 is connected to the collector of the power switch tube S1 and the emitter of the power switch tube S2; one end of the filter inductor C2 is connected to the collector of the power switch tube S1, and the other end is connected to the emitter of the power switch tube S2, the other end of the filter capacitor C3, and the energy storage power supply U s The negative pole of the DC bus support capacitor C dc The other end of the grid-connected inverter is connected to the negative pole of the input terminal.

[0038] The voltage across the filter capacitor C1 is denoted as u1, the voltage across the filter capacitor C2 is denoted as u2, the voltage across the filter capacitor C3 is denoted as u3, the current flowing through the filter capacitor C1 is denoted as i1, and the current flowing through the filter inductor L is denoted as i2. A The current is denoted as i A .

[0039] Reference Figure 3 The present invention also discloses a control method for a secondary ripple suppression circuit applied to an energy storage system, the method comprising the following steps:

[0040] Step S01, subtracting the voltage reference value of the filter capacitor C2 from the voltage of the filter capacitor C2 to obtain a voltage deviation value of the filter capacitor C2;

[0041] Step S02, inputting the voltage deviation value of the filter capacitor C2 into the controller G1(s), and multiplying the output of the controller G1(s) by the voltage differential value of the filter capacitor C1;

[0042] Among them, the controller G1(s) is a PI controller, and its transfer function is:

[0043]

[0044] Among them, K1p and K 1i are the PI parameters of the controller respectively. In the transfer function, "s" usually represents the complex variable in the Laplace transform.

[0045] Step S03, adding the result of the multiplication in step S02, the DC component reference value of the voltage of the filter capacitor C3 and the secondary ripple component reference value of the voltage of the filter capacitor C3 to obtain a voltage reference value of the filter capacitor C3;

[0046] Specifically, the secondary ripple voltage reference value of the filter capacitor C3 is obtained by filtering the voltage of the filter capacitor C1 through a bandpass filter with twice the output frequency and then inverting it.

[0047] Step S04, subtracting the voltage reference value of the filter capacitor C3 from the voltage of the filter capacitor C3 to obtain a voltage deviation value of the filter capacitor C3;

[0048] Step S05, inputting the voltage deviation value of the filter capacitor C3 into the controller G2(s), and then obtaining the modulation signals of the switch tube S1 and the switch tube S2 through the PWM modulator.

[0049] The controller G2(s) is a parallel combination of an integrator and a bandpass filter, and its transfer function is:

[0050]

[0051] Among them, K 2i is the adjustment coefficient of the integrator, ξ is the equivalent quality factor of the bandpass filter, and ω is the AC output frequency of the inverter.

[0052] In addition, the voltage u1 across the filter capacitor C1, the voltage u2 across the filter capacitor C2, and the voltage u3 across the filter capacitor C3 are regulated by controlling the on and off of the switch tubes S1 and S2 to suppress the secondary ripple on the DC side.

[0053] In one embodiment of the invention, the DC component reference value of the voltage of the filter capacitor C3 is The determination process is as follows:

[0054] For a single-phase inverter, after modulation by m(t), the current on the DC side is:

[0055]

[0056] Among them, i ac is the output current of the inverter, M is the modulation ratio of the inverter, is the impedance angle of the inverter output load, I m is the inverter output current i ac The amplitude, I dcis the DC side current i dc The DC component, i r is the DC side current i dc The secondary ripple component.

[0057] Assume that capacitor C3 is small enough to absorb any secondary ripple current. Only the switching frequency current from the suppression circuit flows into capacitor C3. In order to filter out all secondary ripple in the DC side current, the inductor current i A Must meet:

[0058]

[0059] In order to eliminate the secondary ripple voltage on the main DC bus, the following conditions should be met:

[0060]

[0061] Since the voltage u3 of capacitor C3 is required to be always positive, the DC component u3 of the voltage 3-0 satisfy:

[0062]

[0063] Therefore, the DC component reference value of the voltage of the filter capacitor C3 is Can be set to:

[0064]

[0065] Where k is u 3-0 with|u 3-2ω |ratio, k>1.

[0066] In summary, the secondary ripple suppression circuit and control method provided by the present invention can achieve complete absorption of secondary ripples, greatly reduce the volume of the filter components required in the circuit, and improve the power density of the system; there is no need to change the original inverter structure, and it can work by simply connecting in parallel on the DC side of the inverter, realizing hot-pluggable operation, and having no effect on the AC side of the inverter. The secondary ripple power is only transmitted between the AC side of the inverter and the branch, thereby improving the service life of the power supply and the operating stability of the system. In addition, the secondary ripple suppression circuit provided requires fewer devices, only 2 power switch tubes, 3 capacitors and 1 inductor, with simple control and low loss.

[0067] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A control method for a secondary ripple suppression circuit applied to an energy storage system, characterized in that: The method comprises the following steps: Step S01, subtracting the voltage reference value of the filter capacitor C2 from the voltage of the filter capacitor C2 to obtain a voltage deviation value of the filter capacitor C2; Step S02, inputting the voltage deviation value of the filter capacitor C2 into the controller G1(s), and multiplying the output of the controller G1(s) by the voltage differential value of the filter capacitor C1; Step S03, adding the result of the multiplication in step S02, the DC component reference value of the voltage of the filter capacitor C3 and the secondary ripple component reference value of the voltage of the filter capacitor C3 to obtain a voltage reference value of the filter capacitor C3; Step S04, subtracting the voltage reference value of the filter capacitor C3 from the voltage of the filter capacitor C3 to obtain a voltage deviation value of the filter capacitor C3; Step S05, inputting the voltage deviation value of the filter capacitor C3 into the controller G2(s), and then obtaining the modulation signals of the switch tube S1 and the switch tube S2 through the PWM modulator; The secondary ripple suppression circuit includes: filter capacitor C1, filter capacitor C2, filter capacitor C3, DC bus support capacitor C dc , power switch tube S1, power switch tube S2, filter inductor L A , Energy storage power supply U s , grid-connected inverter and control circuit; One end of the filter capacitor C1 is connected to the energy storage power supply U s The positive pole of the DC bus support capacitor C dc One end is connected to the positive pole of the grid-connected inverter input terminal, and the other end is connected to the filter inductor L A One end of the filter capacitor C3; filter inductor L A The other end of the filter inductor C2 is connected to the collector of the power switch tube S1 and the emitter of the power switch tube S2; one end of the filter inductor C2 is connected to the collector of the power switch tube S1, and the other end is connected to the emitter of the power switch tube S2, the other end of the filter capacitor C3, and the energy storage power supply U s The negative pole of the DC bus support capacitor C dc The other end of the grid-connected inverter is connected to the negative pole of the input terminal.

2. The control method of a secondary ripple suppression circuit applied to an energy storage system according to claim 1, characterized in that: The voltage u1 across the filter capacitor C1, the voltage u2 across the filter capacitor C2, and the voltage u3 across the filter capacitor C3 are regulated by controlling the on and off of the switch tubes S1 and S2 to suppress the secondary ripple on the DC side.

3. The control method of a secondary ripple suppression circuit applied to an energy storage system according to claim 1, characterized in that: The controller G1(s) in step S02 is a PI controller, and its transfer function is: Among them, K 1p and K 1i are the PI parameters of controller G1(s) respectively.

4. The control method of a secondary ripple suppression circuit applied to an energy storage system according to claim 1, characterized in that: The secondary ripple voltage reference value of the filter capacitor C3 in step S03 is obtained by filtering the voltage of the filter capacitor C1 through a bandpass filter with twice the output frequency and then inverting it.

5. The control method of a secondary ripple suppression circuit applied to an energy storage system according to claim 1, characterized in that: The controller G2(s) in step S05 is a parallel connection of an integrator and a bandpass filter, and its transfer function is: Among them, K 2i is the adjustment coefficient of the integrator, ξ is the equivalent quality factor of the bandpass filter, and ω is the AC output frequency of the inverter.

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