Energy storage battery ripple current suppression circuit and control method thereof

Abstract

The invention discloses an energy storage battery ripple current suppression circuit and a control method thereof, and belongs to the technical field of energy storage. The energy storage converter is composed of a DC / AC conversion circuit and is used for carrying out DC / AC conversion on the output current signal of the energy storage battery to obtain target alternating current and merging the target alternating current into a power grid; and the active filter is connected between the energy storage battery and the energy storage converter and is used for carrying out filtering and phase correction on the output current signal of the energy storage battery to obtain a target compensation signal so as to suppress the ripple current of the energy storage converter on the direct current side by using the target compensation signal and the detection control circuit. The circuit can reduce the size and the manufacturing cost of the energy storage system. Moreover, the circuit can restrain the ripple fluctuation of the DC bus current of the battery BAT + BAT-connected with the DC / AC conversion circuit of the energy storage converter, and prolongs the service life of the energy storage battery.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and particularly relates to a ripple current suppression circuit for an energy storage battery and a control method thereof. Background Art

[0002] In an energy storage system, an energy storage battery and an energy storage converter are usually provided. When the energy storage converter is operating, there will be power fluctuations on the DC bus of the energy storage system, and its frequency is a double-frequency component or a six-frequency component. The power fluctuations on the DC bus will bring additional power losses to the energy storage battery and affect the service life of the energy storage battery.

[0003] In an energy storage system, it is usually required that the current ripple rate of the energy storage converter output is less than 3%. To meet this requirement, the current on the AC side of the energy storage converter is mainly controlled by relevant control strategies. However, there will still be certain power fluctuations on the DC bus under this control method. To further suppress the power fluctuations on the DC bus, a CLC (Capacitor Inductor Capacitor) filter is also connected in series between the energy storage battery and the energy storage converter to suppress the current fluctuations on the input line of the energy storage battery. However, the inductor of the CLC filter requires a large bias inductance, which will result in a large magnetic core of the inductor in the CLC filter and a large number of turns of the coil must be set, thus resulting in a large volume of the energy storage system and high manufacturing costs. At present, there is no relatively effective solution to this technical problem.

[0004] Therefore, how to reduce the volume and manufacturing costs of the energy storage system is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a ripple current suppression circuit for an energy storage battery and a control method thereof to solve the technical problems of large volume and high manufacturing costs of the existing energy storage system. The specific solutions are as follows:

[0006] To solve the above technical problem, the present invention provides a ripple current suppression circuit for an energy storage battery, including:

[0007] An energy storage battery;

[0008] An energy storage converter composed of a DC / AC conversion circuit, which is used to perform DC / AC conversion on the output current signal of the energy storage battery to obtain a target alternating current and incorporate the target alternating current into the power grid;

[0009] An active filter connected between the energy storage battery and the energy storage converter is used to filter the output current signal of the energy storage battery to obtain a target filtered signal, and perform phase correction on the target filtered signal to obtain a target compensation signal, so as to use the target compensation signal and the detection control circuit to suppress the ripple current on the DC side of the energy storage converter.

[0010] Preferably, the active filter includes: a first current sensor, a second current sensor, a first NMOS transistor, a second NMOS transistor, an inductor and a capacitor;

[0011] Wherein, the first end of the first current sensor is connected to the positive electrode of the energy storage battery, the second end of the first current sensor is respectively connected to the DC+ end of the DC / AC conversion circuit and the drain of the first NMOS transistor, the source of the first NMOS transistor is respectively connected to the first end of the inductor and the drain of the second NMOS transistor, the second end of the inductor is connected to the first end of the second current sensor, the second end of the second current sensor is connected to the first end of the capacitor, the second end of the capacitor is connected to the DC- end of the DC / AC conversion circuit, and the source of the second NMOS transistor is respectively connected to the negative electrode of the energy storage battery and the second end of the capacitor.

[0012] In order to solve the above technical problems, the present invention also provides a control method for an energy storage battery ripple current suppression circuit, which is applied to the active filter in an energy storage battery ripple current suppression circuit disclosed above, and includes:

[0013] Filter the output current signal of the energy storage battery to obtain a target filtered signal, and perform phase correction on the target filtered signal to obtain a target compensation signal, so as to use the target compensation signal and the detection control circuit to suppress the ripple current on the DC side of the energy storage converter.

[0014] Preferably, when the active filter includes: a first current sensor, a second current sensor, a first NMOS transistor, a second NMOS transistor, an inductor and a capacitor; and a first end of the first current sensor is connected to the positive electrode of the energy storage battery, a second end of the first current sensor is respectively connected to the DC+ end of the DC / AC conversion circuit and the drain of the first NMOS transistor, a source of the first NMOS transistor is respectively connected to a first end of the inductor and the drain of the second NMOS transistor, a second end of the inductor is connected to a first end of the second current sensor, a second end of the second current sensor is connected to a first end of the capacitor, a second end of the capacitor is connected to the DC- end of the DC / AC conversion circuit, and a source of the second NMOS transistor is respectively connected to the negative electrode of the energy storage battery and the second end of the capacitor; filtering the output current signal of the energy storage battery to obtain a target filtering signal, and performing phase correction on the target filtering signal to obtain a target compensation signal, so as to use the target compensation signal and the detection control circuit to suppress the ripple current on the DC side of the energy storage converter, including:

[0015] Obtain a current detection value of the first current sensor to obtain a first detection signal;

[0016] Perform band-pass filtering on the first detection signal to obtain the target filtering signal, and perform phase correction on the target filtering signal by using a phase compensator to obtain a reference command signal;

[0017] Obtain a current detection value of the second current sensor to obtain a second detection signal, and obtain a difference between the second detection signal and the reference command signal to obtain a target difference;

[0018] Process the target difference by using a PI regulator or a quasi-resonant controller to obtain a first processed signal;

[0019] Determine a first modulation signal and a second modulation signal that are complementary to each other according to the first processed signal, and use the first modulation signal and the second modulation signal sent by the detection control circuit to control the first NMOS transistor and the second NMOS transistor respectively, so as to compensate for the ripple current on the DC side of the energy storage converter.

[0020] Preferably, after processing the target difference by using a PI regulator or a quasi-resonant controller to obtain a first processed signal, it further includes:

[0021] Obtain a difference between an actual voltage value and a preset voltage value of the capacitor to obtain a voltage difference;

[0022] Process the voltage difference using the PI regulator or the quasi-resonant controller to obtain a second processed signal;

[0023] Correspondingly, determining a first modulation signal and a second modulation signal that are complementary to each other according to the first processed signal, and using the first modulation signal and the second modulation signal sent by the detection control circuit to control the first NMOS transistor and the second NMOS transistor respectively to compensate for the ripple current on the DC side of the energy storage converter includes:

[0024] Determine the first modulation signal and the second modulation signal that are complementary to each other according to the first processed signal and the second processed signal, and use the first modulation signal and the second modulation signal sent by the detection control circuit to control the first NMOS transistor and the second NMOS transistor respectively to compensate for the ripple current on the DC side of the energy storage converter.

[0025] Preferably, the actual voltage value of the capacitor is less than the terminal voltage of the energy storage battery.

[0026] Preferably, performing band-pass filtering on the first detection signal to obtain the target filtered signal includes:

[0027] Perform band-pass filtering on the first detection signal using a target band-pass filter to obtain the target filtered signal; the target band-pass filter is a filter formed by connecting a low-pass filter and a high-pass filter in series.

[0028] Preferably, both the target band-pass filter and the phase compensator are implemented by a DSP chip.

[0029] Preferably, when the DC / AC conversion circuit is an H-bridge cascade topology, the lower limit value and the upper limit value of the cut-off frequency of the target band-pass filter are 75 Hz and 200 Hz respectively; when the DC / AC conversion circuit is a three-phase three-level DC / AC topology, the lower limit value and the upper limit value of the cut-off frequency of the target band-pass filter are 100 Hz and 500 Hz respectively.

[0030] Preferably, performing phase correction on the target filtered signal using a phase compensator to obtain a reference command signal includes:

[0031] When the DC / AC conversion circuit is an H-bridge cascade topology, it is determined that the target filtered signal is a second harmonic component, use Matlab software to determine the phase shift of the target band-pass filter at the second harmonic component to obtain a first phase shift, and use the phase compensator to perform phase correction on the first phase shift to obtain the reference command signal;

[0032] When the DC / AC conversion circuit is a three-phase three-level DC / AC topology, it is determined that the target filter signal is a sixth harmonic component. The phase shift of the target band-pass filter at the sixth harmonic component is determined using Matlab software to obtain a second phase shift, and the phase compensator is used to correct the phase of the second phase shift to obtain the reference command signal.

[0033] Beneficial effects: In the energy storage battery ripple current suppression circuit provided by the present invention, there are an energy storage battery, an energy storage converter, and an active filter. Among them, the energy storage converter is composed of a DC / AC conversion circuit, which is used to perform DC / AC conversion on the output current signal of the energy storage battery to obtain a target alternating current and incorporate the target alternating current into the power grid. The active filter is connected between the energy storage battery and the energy storage converter, and is used to filter the output current signal of the energy storage battery to obtain a target filter signal, and correct the phase of the target filter signal to obtain a target compensation signal, so as to use the target compensation signal and the detection control circuit to suppress the ripple current on the DC side of the energy storage converter.

[0034] Because the second harmonic component or the sixth harmonic component existing on the DC bus of the DC / AC conversion circuit in the energy storage converter is not particularly large, based on this attribute characteristic of the DC bus in the energy storage system, an active filter can be used to suppress the ripple current on the DC side of the energy storage converter. Since the active filter mainly relies on the compensation current to suppress the ripple current and does not rely on the inductive characteristics of the inductor to achieve the filtering function, it is possible to avoid setting an inductor with a large bias inductance in the energy storage system, thereby reducing the volume and cost of the energy storage system. And because this circuit can suppress the ripple current on the DC side of the energy storage converter and avoid the power fluctuation on the DC bus of the DC / AC conversion circuit in the energy storage converter, it can also extend the service life of the energy storage battery. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0036] Figure 1 It is a structural diagram of an energy storage battery ripple current suppression circuit provided by an embodiment of the present invention;

[0037] Figure 2 It is a structural diagram of another energy storage battery ripple current suppression circuit provided by an embodiment of the present invention;

[0038] Figure 3 Schematic diagram of the principle when obtaining a reference instruction signal;

[0039] Figure 4 Schematic diagram of the principle for determining a modulation signal provided by an embodiment of the present invention;

[0040] Figure 5 Another schematic diagram of the principle for determining a modulation signal provided by an embodiment of the present invention;

[0041] Figure 6 For determining the first modulation signal by using the modulation signal Umod and the triangular carrier signal Carry Schematic diagram at that time. Specific implementation manners

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] Please refer to Figure 1 , Figure 1 A structural diagram of a ripple current suppression circuit for an energy storage battery provided by an embodiment of the present invention. The circuit includes:

[0044] Energy storage battery 11;

[0045] An energy storage converter 13 composed of a DC / AC conversion circuit, configured to perform DC / AC conversion on the output current signal of the energy storage battery 11 to obtain a target alternating current and incorporate the target alternating current into the power grid;

[0046] An active filter 12 connected between the energy storage battery 11 and the energy storage converter 13, configured to filter the output current signal of the energy storage battery 11 to obtain a target filtered signal, and perform phase correction on the target filtered signal to obtain a target compensation signal, so as to use the target compensation signal and the detection control circuit to suppress the ripple current on the DC side of the energy storage converter 13.

[0047] In this embodiment, a ripple current suppression circuit for an energy storage battery is provided. By using this circuit, the technical problems of large volume and high manufacturing cost of the existing energy storage system can be solved. In the ripple current suppression circuit of the energy storage battery 11, an energy storage battery 11, an energy storage converter 13, and an active filter 12 are provided.

[0048] Among them, the energy storage converter 13 is composed of a DC / AC conversion circuit. The energy storage converter 13 is used to perform DC / AC conversion on the output current signal of the energy storage battery 11 to obtain a target alternating current and incorporate the target alternating current into the power grid. That is to say, the energy storage converter 13 is used to convert the direct current output by the energy storage battery 11 into a target alternating current. After the energy storage converter 13 converts the direct current output by the energy storage battery 11 into a target alternating current, it will incorporate the target alternating current into the power grid.

[0049] It can be understood that in practical applications, due to environmental factors and the influence of hardware devices, there will inevitably be direct current components and alternating current components on the connection line between the energy storage battery 11 and the energy storage converter 13. That is to say, there will be a certain power fluctuation on the DC bus of the energy storage system, and its frequency is usually a double-frequency component or a six-frequency component. The power fluctuation on the DC bus will bring additional power loss to the energy storage battery 11 and affect the service life of the energy storage battery 11. To avoid this problem, in this embodiment, an active filter 12 is connected between the energy storage battery 11 and the energy storage converter 13, and the active filter 12 is used to filter the output current signal of the energy storage battery 11 to obtain a target filtered signal. Among them, the target filtered signal is generally a double-frequency component or a six-frequency component.

[0050] After obtaining the target filtered signal, the active filter 12 is used to perform phase correction on the target filtered signal to obtain a target compensation signal. That is to say, the target compensation signal is used to compensate the alternating current component on the DC bus of the energy storage system, so that the purpose of suppressing the ripple current on the DC side of the energy storage converter 13 can be achieved by using the target compensation signal. Compared with the prior art, since the active filter 12 mainly relies on the compensation current to suppress the ripple current and does not rely on the inductive characteristics of the inductor to achieve the filtering function, it is possible to avoid setting an inductor with a large bias inductance in the energy storage system, thereby reducing the volume and cost of the energy storage system.

[0051] It should be noted that in practical applications, the active filter 12 can be set to any circuit structure that conforms to the attribute characteristics of the active filter 12, as long as it can achieve the control logic that the active filter 12 can execute in this embodiment.

[0052] In addition, in this embodiment, after suppressing the ripple current on the DC side of the energy storage converter 13, it is possible to avoid the power fluctuation existing on the DC bus of the DC / AC conversion circuit in the energy storage converter 13, thereby avoiding the power loss brought to the energy storage battery 11 due to the power fluctuation on the DC bus, and thus being able to extend the service life of the energy storage battery 11.

[0053] Based on the above embodiments, the technical solution is further described and optimized in this embodiment. Please refer to Figure 2 , Figure 2 which is a structural diagram of another ripple current suppression circuit for an energy storage battery provided by an embodiment of the present invention. As a preferred implementation manner, the above active filter 12 includes: a first current sensor CT1, a second current sensor CT2, a first NMOS transistor Q1, a second NMOS transistor Q2, an inductor L, and a capacitor C;

[0054] Among them, the first end of the first current sensor CT1 is connected to the positive electrode BAT+ of the energy storage battery. The second end of the first current sensor CT1 is respectively connected to the DC+ end of the DC / AC conversion circuit and the drain of the first NMOS transistor Q1. The source of the first NMOS transistor Q1 is respectively connected to the first end of the inductor L and the drain of the second NMOS transistor Q2. The second end of the inductor L is connected to the first end of the second current sensor CT2. The second end of the second current sensor CT2 is connected to the first end of the capacitor C. The second end of the capacitor C is connected to the DC- end of the DC / AC conversion circuit. The source of the second NMOS transistor Q2 is respectively connected to the negative electrode BAT- of the energy storage battery and the second end of the capacitor C.

[0055] In this embodiment, the structure of the active filter 12 is specifically described. In this active filter 12, it is mainly built by using two NMOS transistors (N Metal Oxide Semiconductor), an inductor L, and a capacitor C. The purpose of setting the first current sensor CT1 is to detect the current in the connection line between the energy storage battery and the energy storage converter. The purpose of setting the second current sensor CT2 is to measure the current flowing through the inductor L to facilitate phase correction of the target filter signal in the subsequent process.

[0056] It should be noted that in Figure 2 the shown ripple current suppression circuit of the energy storage battery, the control signals of the first NMOS transistor Q1 and the second NMOS transistor Q2 are both provided by the control circuit in the DSP chip (Digital Signal Processor). And, in Figure 2 the AC signal connected to the rear stage of the DC / AC conversion circuit represents that the DC / AC conversion circuit converts the direct current output by the energy storage battery into three-phase alternating current.

[0057] Obviously, due to this setting method of the active filter, the structure is simple and fewer electronic devices are used. This can not only reduce the structural complexity of the active filter, but also reduce the design cost required for the energy storage system.

[0058] Correspondingly, an embodiment of the present invention further provides a control method for a ripple current suppression circuit of a energy storage battery, which is applied to an active filter in the ripple current suppression circuit of a energy storage battery disclosed above, and includes:

[0059] Filter the output current signal of the energy storage battery to obtain a target filtered signal, and perform phase correction on the target filtered signal to obtain a target compensation signal, so as to suppress the ripple current on the DC side of the energy storage converter by using the target compensation signal and the detection control circuit.

[0060] In this embodiment, a control method for a ripple current suppression circuit of a energy storage battery is provided. This method is specifically described with the active filter in the ripple current suppression circuit of a energy storage battery as the execution subject. This method can refer to the relevant descriptions and records of the active filter in the foregoing embodiments, and will not be elaborated here.

[0061] The control method for a ripple current suppression circuit of a energy storage battery provided by the embodiment of the present invention has the beneficial effects of the ripple current suppression circuit of a energy storage battery disclosed above.

[0062] Based on the above embodiments, this embodiment further illustrates and optimizes the technical solution. As a preferred implementation manner, when the active filter includes: a first current sensor, a second current sensor, a first NMOS transistor, a second NMOS transistor, an inductor, and a capacitor; and the first end of the first current sensor is connected to the positive electrode of the energy storage battery, the second end of the first current sensor is respectively connected to the DC+ end of the DC / AC conversion circuit and the drain of the first NMOS transistor, the source of the first NMOS transistor is respectively connected to the first end of the inductor and the drain of the second NMOS transistor, the second end of the inductor is connected to the first end of the second current sensor, the second end of the second current sensor is connected to the first end of the capacitor, the second end of the capacitor is connected to the DC- end of the DC / AC conversion circuit, and the source of the second NMOS transistor is respectively connected to the negative electrode of the energy storage battery and the second end of the capacitor; the above steps: filter the output current signal of the energy storage battery to obtain a target filtered signal, and perform phase correction on the target filtered signal to obtain a target compensation signal, so as to suppress the ripple current on the DC side of the energy storage converter by using the target compensation signal and the detection control circuit, include:

[0063] Obtain the current detection value of the first current sensor to obtain a first detection signal;

[0064] Perform band-pass filtering on the first detection signal to obtain a target filtered signal, and perform phase correction on the target filtered signal by using a phase compensator to obtain a reference command signal;

[0065] Obtain the current detection value of the second current sensor to obtain a second detection signal, and calculate the difference between the second detection signal and the reference command signal to obtain a target difference;

[0066] Use a PI regulator or a quasi-resonant controller to process the target difference to obtain a first processed signal;

[0067] Determine complementary first and second modulation signals according to the first processed signal, so as to use the first and second modulation signals sent by the detection control circuit to control the first NMOS transistor and the second NMOS transistor respectively, so as to compensate for the ripple current on the DC side of the energy storage converter.

[0068] In this embodiment, taking Figure 2 the shown active filter as an example, the control logic executed by the active filter is specifically described. When filtering the output current signal of the energy storage battery to obtain a target filtered signal, first, use the first current sensor CT1 to detect the current on the connection line between the energy storage battery (BAT+ and BAT- are the positive and negative electrodes of the energy storage battery respectively) and the energy storage converter. At this time, the current detected by the first current sensor CT1 is the first detection signal. Among them, the first detection signal includes both the DC component on the DC bus and the AC component on the DC bus. Secondly, perform band-pass filtering on the first detection signal to obtain a target filtered signal. Among them, the target filtered signal is the AC component extracted from the DC bus, that is, the second harmonic component or the sixth harmonic component. Then, use a phase compensator to perform phase correction on the target filtered signal to obtain a reference command signal for compensating the AC component on the DC bus.

[0069] Please refer to Figure 3 , Figure 3 which is a schematic diagram of the principle when obtaining the reference command signal. When determining the reference command signal, first, use the first current sensor CT1 to detect the current on the connection line between the energy storage battery and the energy storage converter to obtain a first detection signal i1. Secondly, use a band-pass filter (BPF, Band Pass Filter) to perform band-pass filtering on the first detection signal i1 to obtain a target filtered signal, and use a phase compensator to perform phase correction on the target filtered signal to obtain a reference command signal for compensating the AC component on the DC bus 。

[0070] After that, obtain the current detection value of the second current sensor CT2 to obtain a second detection signal, and calculate the difference between the second detection signal and the reference command signal to obtain a target difference. Among them, the target difference can represent the difference between the calculated current amount and the actual current amount on the DC bus.

[0071] After obtaining the target difference, a PI (Proportional Integral) regulator or a quasi-resonant controller is used to process the target difference to obtain a first processed signal. Herein, the purpose of obtaining the first processed signal is to use the first processed signal to achieve the purpose of tracking the true current amount on the DC bus. Finally, the first processed signal is used to determine complementary first and second modulation signals, and the first and second NMOS transistors Q1 and Q2 are controlled by the first and second modulation signals respectively, so that when harmonic current flows through the first current sensor CT1, the current magnitude flowing through the second current sensor CT2 is controlled to be the same as the magnitude of the harmonic current flowing through the first current sensor CT1, thereby making the harmonic current on the first current sensor CT1 smaller and smaller and tending to zero, and thus the purpose of compensating the ripple current on the DC side of the energy storage converter can be achieved.

[0072] Please refer to Figure 4 , Figure 4 which is a schematic diagram of the principle when determining the modulation signal provided by the embodiment of the present invention. In Figure 4 , a difference between the second detection signal i2 and the reference command signal is processed by using a PI regulator or a quasi-resonant controller to obtain a first processed signal Umod1. Herein, the first processed signal Umod1 is the modulation signal corresponding to the sum of the first and second modulation signals.

[0073] Obviously, through the technical solution provided by this embodiment, the purpose of compensating the ripple current on the DC side of the energy storage converter can be achieved.

[0074] As a preferred implementation manner, after the above step: using a PI regulator or a quasi-resonant controller to process the target difference to obtain a first processed signal, it further includes:

[0075] Obtaining a voltage difference by obtaining a difference between the actual voltage value of the capacitor and the preset voltage value;

[0076] Using a PI regulator or a quasi-resonant controller to process the voltage difference to obtain a second processed signal;

[0077] Correspondingly, determining complementary first and second modulation signals according to the first processed signal, and using the first and second modulation signals to control the first and second NMOS transistors respectively to compensate the ripple current on the DC side of the energy storage converter, includes:

[0078] Determine a first modulation signal and a second modulation signal that are complementary to each other according to the first processing signal and the second processing signal, and use the first modulation signal and the second modulation signal sent by the detection control circuit to control the first NMOS transistor and the second NMOS transistor respectively, so as to compensate for the ripple current on the DC side of the energy storage converter.

[0079] In this embodiment, in order to better compensate for the ripple current on the DC side of the energy storage converter and ensure the stability of the active filter during operation, the difference between the actual voltage value of the capacitor C and the preset voltage value can also be obtained to get the voltage difference, and the PI regulator or the quasi-resonant controller is used to process the voltage difference to obtain the second processing signal.

[0080] Then, determine a first modulation signal and a second modulation signal that are complementary to each other according to the first processing signal and the second processing signal, and use the first modulation signal and the second modulation signal sent by the detection control circuit to control the first NMOS transistor Q1 and the second NMOS transistor Q2 respectively, so as to compensate for the ripple current on the DC side of the energy storage converter. In this setting mode, the modulation signal for controlling the first NMOS transistor Q1 and the second NMOS transistor Q2 can be generated according to the actual operating state of the active filter, thereby ensuring the stability of the active filter during operation.

[0081] It should be noted that in this embodiment, it is necessary to ensure that the actual voltage value of the capacitor C is less than the terminal voltage of the energy storage battery. Because according to the actual operating conditions of the energy storage system, the actual voltage value of the capacitor C is less than the terminal voltage of the energy storage battery. If the actual voltage value of the capacitor C is equal to or greater than the terminal voltage of the energy storage battery, it means that an abnormality has occurred during the operation of the energy storage system.

[0082] Please refer to Figure 5 , Figure 5 which is a schematic diagram of the principle when determining the modulation signal provided by another embodiment of the present invention. In Figure 5 , first, the PI regulator or the quasi-resonant controller is used to process the difference between the second detection signal i2 and the reference command signal to obtain the first processing signal Umod1; then, the difference between the actual voltage value Uc of the capacitor C and the preset voltage value is obtained to get the voltage difference, and the PI regulator or the quasi-resonant controller is used to process the voltage difference to obtain the second processing signal Umod2; finally, by obtaining the sum value of the first processing signal Umod1 and the second processing signal Umod2, the final modulation signal Umod can be obtained. The modulation signal Umod is the modulation signal corresponding to the sum of the first modulation signal and the second modulation signal.

[0083] Please refer toFigure 6 , Figure 6 Schematic diagram when using the modulation signal Umod and the triangular carrier signal Carry to determine the first modulation signal . As Figure 6 shown, when the modulation signal Umod and the triangular carrier signal Carry are modulated together, the control signal for controlling the first NMOS transistor Q1 in Figure 2 can be obtained, that is, the first modulation signal . Since the control signal (second modulation signal) for controlling the second NMOS transistor is complementary to the first modulation signal, therefore, according to the first modulation signal , the second modulation signal can be obtained. It should be noted that in Figure 6 , the horizontal axis represents time t, and the vertical axis represents frequency f.

[0084] Obviously, through the technical solution provided in this embodiment, the effect of compensating the ripple current on the DC side of the energy storage converter can be improved.

[0085] As a preferred implementation manner, the above step: performing band-pass filtering on the first detection signal to obtain a target filtered signal, includes:

[0086] Performing band-pass filtering on the first detection signal by using a target band-pass filter to obtain a target filtered signal; the target band-pass filter is a filter formed by connecting a low-pass filter and a high-pass filter in series.

[0087] In this embodiment, in order to improve the band-pass filtering effect on the first detection signal, the target band-pass filter is set in the form of a series connection of a low-pass filter and a high-pass filter. Because in this setting method, the target band-pass filter can achieve more accurate frequency selection, and thus the filtering effect of the target band-pass filter can be further improved.

[0088] Among them, the transfer function of the target band-pass filter is:

[0089] ;

[0090] In the formula, is the complex frequency, which is a variable in the complex number domain, is the cut-off frequency of the low-pass filter, is the cut-off frequency of the high-pass filter.

[0091] As a preferred implementation manner, both the target band-pass filter and the phase compensator are implemented by a DSP chip.

[0092] In this embodiment, in order to reduce the design cost of the energy storage system, both the target band-pass filter and the phase compensator are implemented by a DSP chip. Since the DSP chip has a high degree of integration and programmability, and its setting cost is relatively low, in this embodiment, the control logic executed by the target band-pass filter and the phase compensator can be implemented using the DSP chip.

[0093] Specifically, when both the target band-pass filter and the phase compensator are implemented by a DSP chip, after the first current sensor detects the current signal on the DC bus, through the sampling and quantization of the DSP chip, the digital signal corresponding to the analog signal detected by the first current sensor can be obtained. Then, by performing a Z-transform on the transfer functions of the target band-pass filter and the phase compensator, the transfer functions of the target band-pass filter and the phase compensator in the Z domain can be obtained; afterwards, according to the transfer functions of the target band-pass filter and the phase compensator in the Z domain, the difference equations corresponding to the target band-pass filter and the phase compensator can be obtained. After obtaining the difference equations corresponding to the target band-pass filter and the phase compensator, the functional logic executed by the target band-pass filter and the phase compensator can be implemented by the DSP chip in the digital system.

[0094] In this embodiment, the upper and lower limit values of the cut-off frequency of the target band-pass filter vary according to the different topological structures of the DC / AC conversion circuit in the energy storage inverter. Specifically, when the DC / AC conversion circuit is an H-bridge cascaded topological structure, the lower and upper limit values of the cut-off frequency of the target band-pass filter are 75 Hz and 200 Hz respectively; when the DC / AC conversion circuit is a three-phase three-level DC / AC topological structure, the lower and upper limit values of the cut-off frequency of the target band-pass filter are 100 Hz and 500 Hz respectively.

[0095] As a preferred implementation manner, the above step: using the phase compensator to perform phase correction on the target filtered signal to obtain a reference command signal, includes:

[0096] When the DC / AC conversion circuit is an H-bridge cascaded topological structure, it is determined that the target filtered signal is a second harmonic component, and Matlab software is used to determine the phase shift of the target band-pass filter at the second harmonic component to obtain a first phase shift, and the phase compensator is used to perform phase correction on the first phase shift to obtain a reference command signal;

[0097] When the DC / AC conversion circuit is a three-phase three-level DC / AC topological structure, it is determined that the target filtered signal is a sixth harmonic component, and Matlab software is used to determine the phase shift of the target band-pass filter at the sixth harmonic component to obtain a second phase shift, and the phase compensator is used to perform phase correction on the second phase shift to obtain a reference command signal.

[0098] In this embodiment, if the DC / AC conversion circuit in the energy storage converter is an H-bridge cascaded topology structure, it indicates that the target filtering signal extracted by the target band-pass filter is a second harmonic component. At this time, the phase shift of the target band-pass filter at the second harmonic component can be calculated through Matlab software, so as to obtain the first phase shift corresponding to the target band-pass filter at the second harmonic component. After obtaining the first phase shift, the phase compensator can be used to correct the first phase shift, so as to obtain a reference command signal for compensating the AC component on the DC bus.

[0099] Similarly, if the DC / AC conversion circuit in the energy storage converter is a three-phase three-level DC / AC topology structure, it indicates that the target filtering signal extracted by the target band-pass filter is a sixth harmonic component. At this time, the phase shift of the target band-pass filter at the sixth harmonic component can be calculated through Matlab software, so as to obtain the second phase shift corresponding to the target band-pass filter at the sixth harmonic component. After obtaining the second phase shift, the phase compensator can be used to correct the second phase shift, so as to obtain a reference command signal for compensating the AC component on the DC bus.

[0100] Among them, when the phase compensator is an advanced phase shift compensation, the transfer function of the phase compensator is as follows:

[0101] ;

[0102] In the formula, is the gain factor, is the complex frequency, which is a variable in the complex number domain.

[0103] When the phase compensator is a lag phase shift compensation, the transfer function of the phase compensator is as follows:

[0104] ;

[0105] In the formula, is the gain factor, is the complex frequency, which is a variable in the complex number domain.

[0106] Obviously, through the technical solution provided in this embodiment, the reference command signal for compensating the AC component on the DC bus can be accurately determined in different application scenarios.

[0107] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other.

[0108] Finally, it should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0109] The above has introduced in detail an energy storage battery ripple current suppression circuit and its control method provided by the present invention. Specific examples are used in this text to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A ripple current suppression circuit for an energy storage battery, characterized in that, Comprising: Energy storage battery; An energy storage inverter composed of a DC / AC conversion circuit, which is used to perform DC / AC conversion on the output current signal of the energy storage battery to obtain a target alternating current and incorporate the target alternating current into the power grid; An active filter connected between the energy storage battery and the energy storage inverter, which is used to filter the output current signal of the energy storage battery to obtain a target filtered signal, and perform phase correction on the target filtered signal to obtain a target compensation signal, so as to use the target compensation signal and the detection control circuit to suppress the ripple current on the DC side of the energy storage inverter.

2. The ripple current suppression circuit of an energy storage battery according to claim 1, characterized in that The active filter includes: a first current sensor, a second current sensor, a first NMOS transistor, a second NMOS transistor, an inductor and a capacitor; Wherein, the first end of the first current sensor is connected to the positive electrode of the energy storage battery, the second end of the first current sensor is respectively connected to the DC+ end of the DC / AC conversion circuit and the drain of the first NMOS transistor, the source of the first NMOS transistor is respectively connected to the first end of the inductor and the drain of the second NMOS transistor, the second end of the inductor is connected to the first end of the second current sensor, the second end of the second current sensor is connected to the first end of the capacitor, the second end of the capacitor is connected to the DC- end of the DC / AC conversion circuit, and the source of the second NMOS transistor is respectively connected to the negative electrode of the energy storage battery and the second end of the capacitor.

3. A control method for a ripple current suppression circuit of a storage battery, characterized in that, The active filter applied to the energy storage battery ripple current suppression circuit according to claim 1 or 2 includes: Filtering the output current signal of the energy storage battery to obtain a target filtered signal, and performing phase correction on the target filtered signal to obtain a target compensation signal, so as to use the target compensation signal and the detection control circuit to suppress the ripple current on the DC side of the energy storage inverter.

4. The control method of a ripple current suppression circuit for an energy storage battery according to claim 3, characterized in that, When the active filter includes: a first current sensor, a second current sensor, a first NMOS transistor, a second NMOS transistor, an inductor and a capacitor; and the first end of the first current sensor is connected to the positive electrode of the energy storage battery, the second end of the first current sensor is respectively connected to the DC+ end of the DC / AC conversion circuit and the drain of the first NMOS transistor, the source of the first NMOS transistor is respectively connected to the first end of the inductor and the drain of the second NMOS transistor, the second end of the inductor is connected to the first end of the second current sensor, the second end of the second current sensor is connected to the first end of the capacitor, the second end of the capacitor is connected to the DC- end of the DC / AC conversion circuit, and the source of the second NMOS transistor is respectively connected to the negative electrode of the energy storage battery and the second end of the capacitor; the filtering the output current signal of the energy storage battery to obtain a target filtered signal, and performing phase correction on the target filtered signal to obtain a target compensation signal, so as to use the target compensation signal and the detection control circuit to suppress the ripple current on the DC side of the energy storage inverter includes: Obtain the current detection value of the first current sensor to get a first detection signal; Perform band-pass filtering on the first detection signal to obtain the target filtered signal, and use a phase compensator to perform phase correction on the target filtered signal to obtain a reference command signal; Obtain the current detection value of the second current sensor to get a second detection signal, and calculate the difference between the second detection signal and the reference command signal to obtain a target difference; Use a PI regulator or a quasi-resonant controller to process the target difference to obtain a first processed signal; Determine mutually complementary first modulation signal and second modulation signal according to the first processed signal, and use the first modulation signal and the second modulation signal sent by the detection control circuit to control the first NMOS transistor and the second NMOS transistor respectively to compensate the ripple current on the DC side of the energy storage converter.

5. A control method for a ripple current suppression circuit of an energy storage battery according to claim 4, characterized in that, After using the PI regulator or the quasi-resonant controller to process the target difference to obtain a first processed signal, it further includes: Calculate the difference between the actual voltage value of the capacitor and the preset voltage value to obtain a voltage difference; Use the PI regulator or the quasi-resonant controller to process the voltage difference to obtain a second processed signal; Correspondingly, the step of determining mutually complementary first modulation signal and second modulation signal according to the first processed signal, and using the first modulation signal and the second modulation signal sent by the detection control circuit to control the first NMOS transistor and the second NMOS transistor respectively to compensate the ripple current on the DC side of the energy storage converter includes: Determine mutually complementary first modulation signal and second modulation signal according to the first processed signal and the second processed signal, and use the first modulation signal and the second modulation signal sent by the detection control circuit to control the first NMOS transistor and the second NMOS transistor respectively to compensate the ripple current on the DC side of the energy storage converter.

6. The control method of a ripple current suppression circuit for an energy storage battery according to claim 5, characterized in that The actual voltage value of the capacitor is less than the terminal voltage of the energy storage battery.

7. The control method of a ripple current suppression circuit for an energy storage battery according to claim 4, characterized in that, The step of performing band-pass filtering on the first detection signal to obtain the target filtered signal includes: Perform band-pass filtering on the first detection signal by using a target band-pass filter to obtain the target filtered signal; the target band-pass filter is a filter formed by connecting a low-pass filter and a high-pass filter in series.

8. The control method of a ripple current suppression circuit for an energy storage battery according to claim 7, characterized in that, Both the target band-pass filter and the phase compensator are implemented by a DSP chip.

9. The control method of a ripple current suppression circuit for an energy storage battery according to claim 7, characterized in that, When the DC / AC conversion circuit is an H-bridge cascade topology, the lower limit value and the upper limit value of the cut-off frequency of the target band-pass filter are 75 Hz and 200 Hz respectively; when the DC / AC conversion circuit is a three-phase three-level DC / AC topology, the lower limit value and the upper limit value of the cut-off frequency of the target band-pass filter are 100 Hz and 500 Hz respectively.

10. The control method of a ripple current suppression circuit for an energy storage battery according to claim 9, characterized in that, The step of using a phase compensator to perform phase correction on the target filtered signal to obtain a reference command signal includes: When the DC / AC conversion circuit is an H-bridge cascaded topology, it is determined that the target filtering signal is a second harmonic component. The phase shift of the target band-pass filter at the second harmonic component is determined using Matlab software to obtain a first phase shift, and the phase compensator is used to perform phase correction on the first phase shift to obtain the reference command signal; When the DC / AC conversion circuit is a three-phase three-level DC / AC topology, it is determined that the target filtering signal is a sixth harmonic component. The phase shift of the target band-pass filter at the sixth harmonic component is determined using Matlab software to obtain a second phase shift, and the phase compensator is used to perform phase correction on the second phase shift to obtain the reference command signal.

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