Discharging method and device of energy storage converter and energy storage converter

Abstract

The embodiment of the invention discloses a discharging method and device of an energy storage converter and the energy storage converter, and the discharging method of the energy storage converter comprises the steps: obtaining a modulation wave signal when the energy storage converter stops working; a switch driving signal is generated according to the modulation wave signal so as to control the on-off state of each switch in the inverter; wherein when a switch in the inverter is controlled to be switched on and off, the direct current capacitor is discharged through the inverter, or the filter capacitor is discharged through the inverter. By adopting the technical scheme, repeated transmission of power on the direct current side and the alternating current side of the energy storage converter is realized, so that residual energy in a direct current capacitor consumed by an original inverter hardware architecture of the energy storage converter is reused, an external discharge circuit is not needed, the cost and the size are remarkably reduced, and meanwhile, the discharge efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a discharge method and device for an energy storage converter, and the energy storage converter. Background Art

[0002] Against the backdrop of the "dual carbon" goals, renewable energy generation has become the primary form of energy substitution and electricity supply worldwide. Within this context, renewable energy sources, represented by wind and solar power, have achieved high penetration in power systems. However, renewable energy sources are intermittent and volatile, and their direct integration into the grid can cause fluctuations in voltage and frequency. Therefore, energy storage converters are often added to facilitate distributed generation power scheduling and to absorb renewable energy output, ensuring stable grid operation.

[0003] Currently, energy storage converters are key devices connecting energy storage battery systems and the power grid. After a power outage, the energy stored in the DC bus capacitors of various energy storage converters causes the capacitors to present very high voltages, posing a risk of electric shock to maintenance and repair personnel. However, natural discharge of energy storage converters requires a very long discharge time and low discharge efficiency. Discharging the bus capacitors by connecting a parallel bleeder circuit to the bus requires controlling the conduction of this circuit during discharge, increasing system cost and size. Summary of the Invention

[0004] The embodiments of the present invention provide a discharge method and device for an energy storage converter, which improves the discharge efficiency of residual energy in the energy storage converter bus, saves system costs, eliminates the need for additional power-consuming devices, and reduces system volume.

[0005] In a first aspect, an embodiment of the present invention provides a discharge method for an energy storage converter, wherein the energy storage converter includes a DC capacitor, an inverter, and a filter; wherein the DC capacitor is connected in parallel to the DC side of the inverter, the filter is electrically connected to the AC side of the inverter, and the filter includes a filter capacitor;

[0006] The discharging method of the energy storage converter includes:

[0007] When the energy storage converter stops working, obtaining a modulation wave signal;

[0008] A switch drive signal is generated according to the modulated wave signal to control the on / off state of each switch in the inverter; wherein, when controlling the on / off state of the switches in the inverter, the DC capacitor is discharged through the inverter, or the filter capacitor is discharged through the inverter.

[0009] Optionally, the discharging method further includes:

[0010] Acquiring the three-phase voltage on the AC side of the inverter in real time;

[0011] The modulated wave signal is adjusted according to the three-phase voltage on the AC side.

[0012] Optionally, before obtaining the modulated wave signal, the following steps are further included:

[0013] Obtaining status information of the energy storage converter; wherein the DC side of the inverter is further provided with a DC contactor, and the AC side of the inverter is further provided with an AC contactor; the status information includes the on-off state of the DC contactor, the on-off state of the AC contactor, the voltage on the DC side of the inverter, and the voltage on the AC side of the inverter;

[0014] When the status information meets the preset conditions, it is determined that the energy storage converter stops working; wherein the preset conditions include that the DC contactor and the AC contactor are both in the disconnected state, and the voltage on the DC side is less than the preset DC voltage, and the voltage on the AC side is less than the preset AC voltage.

[0015] Optionally, the discharging method of the energy storage converter further includes:

[0016] Obtaining an expected discharge time of the energy storage converter, a stored amount of electricity of the DC capacitor, and a safety voltage of the DC capacitor;

[0017] The modulation wave signal is determined according to the expected discharge time, the stored electricity of the DC capacitor, and the safety voltage of the DC capacitor.

[0018] Optionally, generating a switch drive signal according to the modulated wave signal to control the on / off state of each switch in the inverter includes:

[0019] Determining three-phase modulation waves respectively according to the modulation wave signals;

[0020] The switch driving signal is determined according to the three-phase modulation wave to control the on-off state of each switch in the inverter.

[0021] Optionally, the stage in which the DC capacitor is discharged through the inverter includes a first moment and a second moment, the second moment being located after the first moment; the amplitude of the modulated wave at the first moment is a first amplitude, and the amplitude of the modulated wave at the second moment is a second amplitude; the second amplitude is greater than the first amplitude; and / or,

[0022] The stage in which the filter capacitor is discharged through the inverter includes a third moment and a fourth moment, and the fourth moment is located after the third moment; at the third moment, the amplitude of the modulated wave is the third amplitude, and at the fourth moment, the amplitude of the modulated wave is the fourth amplitude; the third amplitude is greater than the fourth amplitude.

[0023] Optionally, the stage in which the DC capacitor is discharged through the inverter further includes a fifth moment, the fifth moment is located after the second moment, the interval between the first moment and the second moment is equal to the interval between the second moment and the fifth moment; the amplitude of the modulated wave at the fifth moment is a fifth amplitude; the fifth amplitude is greater than the second amplitude; the difference between the first amplitude and the second amplitude is equal to the difference between the second amplitude and the fifth amplitude; and / or,

[0024] The stage in which the filter capacitor discharges through the inverter also includes a sixth moment, the sixth moment is located after the fourth moment, the interval between the third moment and the fourth moment is equal to the interval between the fourth moment and the sixth moment; at the sixth moment, the amplitude of the modulated wave is the sixth amplitude; the fourth amplitude is greater than the sixth amplitude; the difference between the third amplitude and the fourth amplitude is equal to the difference between the fourth amplitude and the sixth amplitude.

[0025] Optionally, the discharging method of the energy storage converter further includes:

[0026] Before the DC capacitor is discharged through each of the switches of the inverter, obtaining a current voltage between two substrates of the DC capacitor;

[0027] When the current voltage is less than or equal to a preset threshold, the switch driving signal is stopped from being generated.

[0028] In a second aspect, an embodiment of the present invention provides a discharge device for an energy storage converter, wherein the energy storage converter includes a DC capacitor, an inverter, and a filter; wherein the DC capacitor is connected in parallel to the DC side of the inverter, the filter is electrically connected to the AC side of the inverter, and the filter includes a filter capacitor;

[0029] The discharging device of the energy storage converter includes: an acquisition module and a control module;

[0030] The acquisition module is used to acquire the modulation wave signal when the energy storage converter stops working;

[0031] The control module is used to generate a switch drive signal according to the modulated wave signal to control the on-off state of each switch in the inverter; wherein, when controlling the on-off state of the switch in the inverter, the DC capacitor is discharged through the inverter, or the filter capacitor is discharged through the inverter.

[0032] In a third aspect, an embodiment of the present invention provides an energy storage converter, comprising: a controller, a DC capacitor, an inverter, and a filter;

[0033] The controller is connected to the inverter, the DC capacitor is connected in parallel to the DC side of the inverter, the filter is electrically connected to the AC side of the inverter, and the filter includes a filter capacitor;

[0034] The controller is used to execute the discharging method of the energy storage converter described in any embodiment of the present invention.

[0035] This embodiment obtains a modulation wave signal when the energy storage converter is in a shutdown state, generates a switch drive signal based on the modulation wave signal, and then controls the on and off of the inverter switch tube, so that the DC capacitor can be discharged through the inverter, or the filter capacitor can be discharged through the inverter, thereby realizing repeated power transmission between the DC side and the AC side of the energy storage converter, thereby reusing the original inverter hardware architecture of the energy storage converter to consume the residual energy in the DC capacitor, eliminating the need for an external discharge circuit, significantly reducing costs and volume, and improving the discharge efficiency and safety of the residual energy of the energy storage converter bus.

[0036] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of 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.

[0038] Figure 1 1 is a structural diagram of an energy storage converter system provided by an embodiment of the present invention;

[0039] Figure 2 This is a flow chart of a discharge method for an energy storage converter provided by an embodiment of the present invention;

[0040] Figure 3 This is a flow chart of another discharge method for an energy storage converter provided by an embodiment of the present invention;

[0041] Figure 4 This is a flow chart of another discharge method for an energy storage converter provided by an embodiment of the present invention;

[0042] Figure 5 This is a flow chart of another discharge method of an energy storage converter provided by an embodiment of the present invention;

[0043] Figure 6 This is a flow chart of another discharge method of an energy storage converter provided by an embodiment of the present invention;

[0044] Figure 7 1 is a waveform diagram of a three-phase modulation wave provided by an embodiment of the present invention;

[0045] Figure 8 1 is a waveform diagram of another three-phase modulation wave provided by an embodiment of the present invention;

[0046] Figure 9 This is a flow chart of another discharging method of an energy storage converter provided by an embodiment of the present invention;

[0047] Figure 10 1 is a structural diagram of a discharge device of an energy storage converter provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be fully described below in conjunction with the drawings in the embodiments of the present invention through specific implementation methods. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Various modifications and changes can be made in the present invention without departing from the spirit or scope of the present invention, which is obvious to those skilled in the art. Therefore, the present invention is intended to cover modifications and changes of the present invention that fall within the scope of the corresponding claims (technical solutions for protection) and their equivalents.

[0049] Furthermore, the words “first”, “second” and similar terms used in the embodiments of the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as “one”, “an” or “the” do not indicate a quantity limitation, but rather indicate the existence of at least one. Words such as “include” or “comprise” mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as “connect” or “connected” are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Up”, “down”, “left”, “right” and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. In addition, descriptions such as “same” and “equal” involved in the embodiments of the present disclosure do not mean that the two objects are exactly the same in size or shape. Approximately the same or approximately equal within a certain error range is allowed.

[0050] It should be noted that the implementation methods provided in the embodiments of the present invention can be combined with each other if there is no contradiction.

[0051] Example 1

[0052] Figure 1 FIG. 1 is a structural diagram of an energy storage converter system provided by an embodiment of the present invention. Figure 1As shown, the energy storage converter system includes a battery 1, a DC contactor 2, an energy storage converter 3, an AC contactor 4, and an AC grid 5. The energy storage converter 3 is a key device connecting the battery 1 and the AC grid 5. Its main functions are as follows: During the charging process, the energy storage converter 3 can convert the AC power input from the AC grid 5 into DC power, safely and efficiently charging the battery 1 and ensuring a smooth and orderly charging process. During the discharge phase, on the contrary, the energy storage converter 3 inverts the DC power output from the battery 1 into AC power, supplying power to the AC grid 5 or the load to meet power usage needs. In addition, the energy storage converter 3 includes a DC capacitor 31, an inverter 32, and a filter 33. Among them, the DC capacitor 31 is connected in parallel to the DC side of the inverter 32. On the one hand, the DC capacitor 31 can smooth and stabilize the voltage on the DC side of the inverter 32. Since the inverter 32 will generate pulsating DC voltage during operation, the DC capacitor 31 can absorb these voltage pulsations through charging and discharging, reduce voltage fluctuations, and ensure that the inverter 32 has a stable DC power input; on the other hand, the DC capacitor 31 can also provide a midpoint voltage through voltage division. The stability of the midpoint voltage directly affects the output quality of the inverter 32. If it is unbalanced, it will cause waveform distortion, increase harmonics, and even threaten the safety of switching devices. Therefore, the DC capacitor 31 divides the DC bus voltage into two parts through two capacitors connected in series, thereby providing a stable midpoint voltage for the inverter 32 as a neutral point reference voltage, ensuring the symmetry and accuracy of the output waveform of the inverter 32. Inverter 32 is a power electronic conversion device that can convert the DC power in DC capacitor 31 into AC power. Its core component is the inverter bridge, which can be composed of multiple power switching devices (such as IGBTs, MOSFETs, etc.). By controlling the on and off sequence and timing of these power switching devices, DC power can be converted into AC power with a certain frequency and amplitude. Filter 33 is electrically connected to the AC side of inverter 32. Filter 33 includes filter capacitor 331 and filter inductor 332. Its main function is to filter out harmonic components in the AC power output by inverter 32 and improve the power quality of the output AC power. Because the inverter uses PWM modulation technology, the AC power it outputs contains a large number of high-order harmonics. If these harmonics are not filtered out, they will have adverse effects on the power grid and other electrical equipment, such as increasing line losses and interfering with communication equipment. Filter 33 can attenuate or suppress harmonics of specific frequencies through filter capacitor 331, making the output AC power closer to an ideal sine wave. The energy storage converter 3 can realize the power regulation function through the inverter 32, and can flexibly adjust the size and direction of the output power according to actual needs, thereby realizing flexible distribution and precise control of electric energy. At the same time, the energy storage converter 3 can also monitor the operating status of the system in real time, and has fault diagnosis and protection functions to ensure the safe and stable operation of the energy storage system.

[0053] However, during the operation of the energy storage converter 3, when the system is in a shutdown or fault state, a large amount of residual energy may be retained on the DC capacitor 31. The traditional passive discharge method relies on the natural dissipation of parasitic resistance, which has the problems of low discharge efficiency and long time consumption, and can easily cause the bus voltage to remain high, threatening the system safety and device life. In order to increase the discharge speed, the existing scheme usually requires an external active discharge circuit (such as a braking resistor or a Buck type discharge module). On the one hand, the additional discharge circuit increases the complexity of the system and requires more electronic components, line connections and control modules, which not only increases the initial construction cost of the system, but also increases the difficulty and cost of subsequent maintenance; on the other hand, these additional components will occupy a certain amount of space, resulting in an increase in the volume of the entire energy storage converter system. In some application scenarios with limited space, such as small distributed energy systems or mobile energy storage equipment, they will face problems such as difficulty in installation or inconvenience in carrying. It can be seen that although the additional discharge circuit can play a certain auxiliary role, it also brings new problems. It not only increases the hardware cost of power devices, heat dissipation structures and control circuits, but also significantly expands the size of the equipment. Especially in industrial, commercial and household energy storage scenarios that pursue high power density and low cost, this design contradiction is more prominent, and there is an urgent need to explore efficient, compact and economical integrated DC capacitor discharge solutions.

[0054] Continue to refer Figure 1 As shown, the energy storage converter 3 provided in this embodiment also includes: a controller 810; the controller 810 is connected to the inverter 32. When the energy storage converter 32 is in a shutdown state, the modulation wave signal is obtained through the controller 810, and a switch drive signal is generated according to the modulation wave signal to control the on and off of the switch tube of the inverter 32, so that the DC capacitor 31 can be discharged through the inverter 32, or the filter capacitor 331 can be discharged through the inverter 32, thereby realizing the repeated transmission of power between the DC side and the AC side of the energy storage converter, thereby reusing the original inverter 32 hardware architecture of the energy storage converter to consume the residual energy in the DC capacitor 31.

[0055] In this embodiment, the controller obtains a modulation wave signal when the energy storage converter is shut down, and generates a switch drive signal based on the modulation wave signal to control the on and off of the inverter switch tube, so that the DC capacitor can be discharged through the inverter, or the filter capacitor can be discharged through the inverter, thereby realizing repeated power transmission between the DC side and the AC side of the energy storage converter, thereby reusing the original inverter hardware architecture of the energy storage converter to consume the residual energy in the DC capacitor, eliminating the need for an external discharge circuit, significantly reducing costs and size, and improving the discharge efficiency and safety of the residual energy of the energy storage converter bus.

[0056] Example 2

[0057] This embodiment provides a discharge method for an energy storage converter. This discharge method for an energy storage converter is applicable to the situation of quickly discharging the DC capacitor of the energy storage converter. It does not require an external discharge circuit, can significantly reduce the cost and volume, and improve the discharge efficiency. The discharge method for the energy storage converter provided in this embodiment can be executed using the discharge device of the energy storage converter provided in an embodiment of the present invention. The device can be implemented by a control module and can be integrated into the energy storage converter. Figure 2 This is a flow chart of a discharge method for an energy storage converter provided by an embodiment of the present invention. Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a discharging method for an energy storage converter, comprising:

[0058] S110 . When the energy storage converter stops working, a modulation wave signal is obtained.

[0059] Specifically, the DC capacitor 31 continuously performs a charge-discharge cycle during the operation of the energy storage converter 3. Under normal operating conditions, the DC capacitor 31 continuously absorbs and releases energy according to the working mode (charging or discharging) and power demand of the energy storage converter 3. However, the charging and discharging process of the DC capacitor 31 is not completed instantly, but there is a certain time constant. Before the energy storage converter 3 stops working due to a shutdown instruction, fault protection or grid abnormality, the DC capacitor 31 may have obtained a certain amount of energy from the grid or other power supply, and suddenly interrupted the process of providing energy to the load. At this time, although the energy storage converter 3 stops working, the charge distribution inside the DC capacitor 31 cannot be changed immediately. The energy stored in the DC capacitor 31 does not have time to be completely released, and the voltage across it will not immediately return to zero, so that the DC capacitor 31 itself is still in a charged state and has residual energy. After the energy storage converter 3 stops working, the on-off state of the inverter 32 in the energy storage converter 3 can be controlled by pulse width modulation, and the residual energy of the DC capacitor 31 is used to generate a three-phase AC voltage on the filter capacitor 331. The three-phase AC voltage can be a sine wave shape.

[0060] Furthermore, according to the actual situation of the energy storage converter 3, a modulation wave signal corresponding to the real-time situation at this moment and capable of discharging the DC capacitor 31 is obtained from the outside world. The modulation wave signal is a reference waveform used to control the on and off of switching devices in the power electronic system. The voltage or current characteristics output by the inverter 32 are controlled by adjusting its parameters. The parameters of the modulation wave signal include at least the modulation wave amplitude and the modulation wave phase, wherein the modulation wave amplitude is positively correlated with the amplitude of the output voltage of the inverter 32, and the modulation wave phase is the same as the phase of the output voltage of the inverter 32.

[0061] S120 , generating a switch driving signal according to the modulation wave signal to control the on / off state of each switch in the inverter.

[0062] When the switch in the inverter is controlled to be on or off, the DC capacitor is discharged through the inverter, or the filter capacitor is discharged through the inverter.

[0063] Specifically, the modulated wave signal can be a signal with certain frequency, amplitude, and phase characteristics. Using a specific modulation technique (e.g., pulse width modulation (PWM) or sinusoidal pulse width modulation (SPWM), the modulated wave signal is compared in real time with a carrier signal (typically a triangular wave or sawtooth wave). When the amplitude of the modulated wave signal is greater than the carrier signal, a high-level switch drive signal is generated; when the amplitude of the modulated wave signal is less than the carrier signal, a low-level switch drive signal is generated. These high- and low-level switch drive signals serve as reference signals in inverter control, controlling the on / off switching of various switching devices (e.g., IGBTs, MOSFETs, etc.) in inverter 32. For example, if inverter 32 is a T-type three-level inverter circuit, when the switch drive signal is high, the switch in the upper arm can be turned on, while the switch in the lower arm can be turned off. When the switch drive signal is low, the switch in the upper arm can be turned off, while the switch in the lower arm can be turned on.

[0064] Furthermore, after the residual energy of the DC capacitor 31 generates a three-phase AC voltage on the filter capacitor 331 for a period of time, the circuit characteristics will naturally converge to a steady state, that is, the output voltage V1 of the DC capacitor 31 through the inverter 32 is the same as the voltage V2 of the filter capacitor 331. At this time, if the switch drive signal controls the conduction state of each switch in the inverter 32, so that the output voltage V1 of the DC capacitor 31 through the inverter 32 increases, V1>V2, and then a current from left to right will be generated on the filter inductor 332, and the DC capacitor 31 discharges the filter capacitor 331 through the inverter 32, combined with the damping effect of the parasitic resistance in the circuit, until the voltage V2 of the filter capacitor 331 rises to be equal to the output voltage V1 of the DC capacitor 31 through the inverter 32 again, thereby entering a new steady state. State; If the switch drive signal controls the conduction state of each switch in the inverter 32, so that the output voltage V1 of the DC capacitor 31 through the inverter 32 decreases, V1 < V2, and then a current from right to left is generated in the filter inductor 332, the filter capacitor 331 discharges the DC capacitor 31 through the inverter 32, combined with the damping effect of the parasitic resistance in the circuit, until the voltage V2 of the filter capacitor 331 decreases to be equal to the output voltage V1 of the DC capacitor 31 through the inverter 32, thereby entering a new steady state. Based on this, by periodically applying the above two switch drive signals to the inverter 32, thereby controlling the conduction state of each switch in the inverter 32 to change alternately, it is possible to achieve repeated power transfer between the DC side and the AC side of the energy storage converter 3. Since each transfer will generate losses in the switch devices and the filter capacitor 331 and the filter inductor 332, the repeated power transfer will generate repeated losses, thereby dissipating the residual energy on the DC capacitor 31 and achieving the purpose of active discharge.

[0065] This embodiment obtains a modulation wave signal when the energy storage converter is in a shutdown state, generates a switch drive signal based on the modulation wave signal, and then controls the on and off of the inverter switch tube, so that the DC capacitor can be discharged through the inverter, or the filter capacitor can be discharged through the inverter, thereby realizing repeated power transmission between the DC side and the AC side of the energy storage converter, thereby reusing the original inverter hardware architecture of the energy storage converter to consume the residual energy in the DC capacitor, eliminating the need for an external discharge circuit, significantly reducing costs and volume, and improving the discharge efficiency and safety of the residual energy of the energy storage converter bus.

[0066] Example 3

[0067] Based on the above embodiments, Figure 3 This is a flow chart of another discharge method of an energy storage converter provided by an embodiment of the present invention. Figure 3 The discharge method of the energy storage converter shown in the figure explains how to adjust the modulation wave signal. Figure 1 and Figure 3 As shown, the discharging method of the energy storage converter includes:

[0068] S210 . Acquire the three-phase voltage on the AC side of the inverter in real time.

[0069] Specifically, the filter 33 may include three filter capacitors 331, and the three filter capacitors 331 correspond to the three-phase circuit connected to the output end of the inverter 32 respectively. The voltage of the three capacitors can be measured respectively by a voltage sensor to obtain the three-phase voltage on the AC side of the inverter 32. Among them, the three-phase voltage on the AC side of the inverter 32 can be that after the on-off state of each switch in the inverter is controlled according to the switch drive signal, the DC capacitor is discharged through the inverter, or the filter capacitor is discharged through the inverter, and then the DC side and the AC side of the energy storage converter 3 enter a new steady state. Since when entering the new steady state, the voltage on the filter capacitor 331 is the same as the output voltage of the inverter 32, and the output voltage of the inverter 32 is controlled by the modulation wave signal, the amplitude of the modulation wave signal determines the output voltage of the inverter 32, therefore, the actual voltage on the filter capacitor 331 represents the actual regulation effect of the modulation wave signal on the voltage of the filter capacitor 331.

[0070] For example, for the three-phase voltage acquisition method on the AC side of the inverter 32, the voltage of each phase can be directly measured by connecting voltage sensors to the three-phase lines on the AC side of the inverter 32 respectively. The voltage sensor can be based on the electromagnetic induction principle (such as an electromagnetic voltage transformer), and utilize the electromagnetic coupling relationship between the primary winding and the secondary winding to convert the high voltage into a low voltage signal that is easy to measure for measurement; it can also adopt the capacitor voltage division principle (such as a capacitor voltage transformer) to obtain the voltage signal by dividing the high-voltage capacitor.

[0071] S220. Adjust the modulation wave signal according to the three-phase voltage on the AC side.

[0072] Specifically, when the DC side and AC side of the energy storage converter 3 enter a new steady state, the three-phase voltage of the filter capacitor 331 is equal to the output three-phase voltage of the AC side of the inverter 32. That is, the three-phase voltage obtained on the AC side also represents the actual control effect of the modulation wave signal on the output voltage of the inverter 32. Therefore, the three-phase voltage data obtained in real time can be used as an important feedback quantity for the closed-loop control of the inverter 32. In the vector control algorithm, the voltage error signal is obtained by comparing the actual measured three-phase voltage with the reference voltage. Then, the modulation wave signal is adjusted by the voltage / current controller according to the error signal, and the switch drive signal used to control the conduction state of the switch of the inverter 32 is dynamically corrected using the adjusted modulation wave signal, so that the actual output voltage of the inverter 32 is closer to the required reference voltage. The amplitude of the output voltage of the inverter 32 is optimized by effectively adjusting the modulation wave signal. Furthermore, by periodically changing the reference voltage and optimizing the modulated wave signal in combination with the three-phase voltage on the AC side, it is possible to achieve repeated transmission of energy between the AC side and the DC side of the energy storage converter 3, thereby generating losses and releasing the energy stored in the bus capacitor of the energy storage converter 3, thereby improving the discharge efficiency of the residual energy of the energy storage converter bus.

[0073] For example, the voltage / current controller can be a proportional-integral controller. If the amplitude of a phase voltage on the AC side is detected to be lower than a given reference voltage, a gain factor related to the voltage error can be introduced to appropriately increase the amplitude of the modulation wave signal of that phase. The gain factor can be dynamically adjusted based on the difference between the actual voltage and the reference voltage, thereby changing the amplitude of the modulation wave signal, thereby affecting the amplitude of the inverter output voltage, bringing it closer to the target value. Because the amplitude of the modulation wave signal determines the amplitude of the output voltage, increasing the amplitude of the modulation wave will increase the pulse width of the inverter 32 output voltage, thereby increasing the effective value of the output voltage and achieving dynamic adjustment of the modulation wave signal.

[0074] S230: When the energy storage converter stops working, obtain a modulation wave signal.

[0075] S240 , generating a switch driving signal according to the modulation wave signal to control the on / off state of each switch in the inverter.

[0076] This embodiment achieves closed-loop control of the energy storage converter's discharge process by acquiring the three-phase voltage on the inverter's AC side in real time and adjusting the modulation wave signal based on the three-phase voltage on the AC side. This improves the control accuracy of the inverter's output voltage and the discharge efficiency of the energy storage converter's busbar residual energy, ensuring stability and reliability during the discharge process.

[0077] Example 4

[0078] Based on the above embodiments, Figure 4 This is a flow chart of another discharge method of an energy storage converter provided by an embodiment of the present invention. Figure 4 The discharge method of the energy storage converter shown in FIG. 1 is described before obtaining the modulation wave signal. Figure 1 and Figure 4 As shown, the discharging method of the energy storage converter includes:

[0079] S310: Obtain status information of the energy storage converter.

[0080] Among them, the DC side of the inverter 32 is also provided with a DC contactor 2, and the AC side of the inverter 32 is also provided with an AC contactor 4; the status information includes the on-off status of the DC contactor 2, the on-off status of the AC contactor 4, the voltage on the DC side of the inverter, and the voltage on the AC side of the inverter.

[0081] Specifically, the DC contactor 2 is a switching device used to control the connection between the battery 1 and the energy storage converter 3. It can serve as a protective element. When a short circuit occurs in the battery pack, the DC contactor 2 can promptly cut off the circuit, preventing damage to the battery 1 due to overcurrent, preventing further expansion of the fault, and protecting the safety of the energy storage converter 3 and other electrical equipment. The DC contactor 2 can also isolate the DC side circuit from the external circuit during maintenance or repair of the energy storage converter 3 to prevent accidental electric shock and circuit misoperation. The AC contactor 4 is a switching device used to control the connection between the AC grid 5 and the energy storage converter 3. When the energy storage converter 3 needs to be connected to the grid for operation, the AC contactor 4 closes, connecting the AC power output by the inverter 32 to the grid, realizing the transmission and exchange of electrical energy. When the energy storage converter 3 needs to be removed from the grid for maintenance, repair, or to respond to an emergency, the AC contactor 4 opens, severing the connection with the AC grid 5, ensuring operational safety and the independence of the equipment.

[0082] The on / off status of the DC contactor 2 and the AC contactor 4 can be obtained by monitoring the signals of their auxiliary contacts. The auxiliary contacts are usually linked to the main contacts. When the main contacts are closed, the auxiliary contacts change state, thereby sending a signal indicating that the contactor is closed. Conversely, when the main contacts are disconnected, the auxiliary contacts return to their initial state, and the corresponding signals also change. Such signals can be electrical signals (such as voltage signals, current signals, etc.), which are sensed and collected by detection elements (such as sensors, relays, etc.) in the control circuit and transmitted to the control system for judgment, thereby obtaining the on / off status of the DC contactor 2 and the AC contactor 4. The voltage on the DC side of the inverter 32 and the voltage on the AC side of the inverter 32 can be achieved by installing a voltage sensor. The voltage sensor transmits the collected analog voltage signal to the analog-to-digital converter in the control system. After the analog-to-digital converter converts the analog signal into a digital signal, the control system can calculate and analyze the DC side voltage and the AC side voltage according to preset algorithms and parameters, thereby obtaining accurate DC side voltage values and AC side voltage values.

[0083] S320: When the status information meets a preset condition, determine that the energy storage converter stops working.

[0084] The preset conditions include that the DC contactor 2 and the AC contactor 4 are both in the disconnected state, the voltage on the DC side is less than the preset DC voltage, and the voltage on the AC side is less than the preset AC voltage.

[0085] Specifically, when the obtained on-off state of the DC contactor 2 is the disconnected state, it indicates that the DC side of the energy storage converter 3 is disconnected from the battery 1; when the obtained on-off state of the AC contactor 4 is the disconnected state, it indicates that the AC side of the energy storage converter 3 is disconnected from the AC grid 5; when the voltage on the DC side is less than the preset DC voltage, it indicates that the battery 1 does not charge the DC side of the energy storage converter 3, further confirming that the battery 1 is disconnected from the DC side of the energy storage converter 3; when the voltage on the AC side is less than the preset AC voltage, it indicates that the AC grid 5 does not charge the AC side of the energy storage converter 3, further confirming that the AC grid 5 is disconnected from the AC side of the energy storage converter 3. By detecting in real time whether the status information of the energy storage converter meets the above-mentioned preset conditions, it is determined whether the energy storage converter 3 is disconnected from the system and stops working. If the status information of the energy storage converter 3 meets the above-mentioned preset conditions, it is determined that the energy storage converter 3 has stopped working, and the active discharge function can be performed; if the status information of the energy storage converter 3 meets the above-mentioned preset conditions, it indicates that the energy storage converter 3 has not stopped working, and the active discharge function is not performed. When the energy storage converter 3 stops working, the active discharge function is turned on, which can effectively avoid electrical accidents caused by the release of electric energy during the operation of the energy storage converter 3, extend the service life of the energy storage converter 3, and ensure the safety of maintenance personnel.

[0086] S330. When the energy storage converter stops working, obtain a modulation wave signal.

[0087] S340 , generating a switch driving signal according to the modulation wave signal to control the on / off state of each switch in the inverter.

[0088] When the switch in the inverter is controlled to be on or off, the DC capacitor is discharged through the inverter, or the filter capacitor is discharged through the inverter.

[0089] In this embodiment, when the status information of the energy storage converter satisfies that both the DC contactor and the AC contactor are in the disconnected state, and the voltage on the DC side is less than a preset DC voltage, and the voltage on the AC side is less than a preset AC voltage, the energy storage converter is determined to stop operating. This avoids electrical accidents caused by the energy storage converter releasing electric energy before it stops operating, ensures the safety of operators, and extends the service life of the energy storage converter.

[0090] Example 5

[0091] Based on the above embodiments, Figure 5 This is a flow chart of another discharge method of an energy storage converter provided by an embodiment of the present invention. Figure 5 The discharge method of the energy storage converter shown in the figure explains how to determine the modulation wave signal. Figure 1 and Figure 5 As shown, the discharging method of the energy storage converter also includes:

[0092] S410: When the energy storage converter stops working, a modulation wave signal is obtained.

[0093] S420: Obtain an expected discharge time of the energy storage converter, a stored quantity of the DC capacitor, and a safety voltage of the DC capacitor.

[0094] Specifically, the stored capacity of DC capacitor 31 refers to the amount of energy currently stored in DC capacitor 31 after the energy storage converter 3 stops operating. The stored capacity of DC capacitor 31 can be represented by the voltage of DC capacitor 31. This capacity can be obtained using a voltage sensor installed on DC capacitor 31. The voltage sensor measures the voltage across DC capacitor 31 and calculates the stored capacity of DC capacitor 31 based on the relationship between the capacitor voltage and the capacity. The safe voltage of DC capacitor 31 refers to the maximum voltage allowed within the access area of maintenance personnel after the energy storage converter 3 stops operating. Exceeding the safe voltage may create a safety hazard if maintenance personnel accidentally touch the energy storage converter 3 during inspection. The expected discharge time refers to the time required by the user or system for the voltage of the DC capacitor 31 within the energy storage converter 3 to drop from the stored capacity to the safe voltage after the energy storage converter 3 stops operating. The expected discharge time can be directly set by the user. According to the maintenance plan of the energy storage converter 3, the expected discharge time can be input through the intelligent control panel. The discharge time of the energy storage converter 3 can also be set by issuing instructions through the power grid dispatching center to meet the needs of power grid outage maintenance.

[0095] For example, the requirements for the discharge of residual energy of DC capacitors in the technical specifications of the energy storage converter of the electrochemical energy storage system are: when the energy storage converter stops working, in the area of contact with maintenance personnel, the DC capacitor voltage needs to be reduced to below 60V or the stored energy of the DC capacitor is less than 20J, and the discharge time of the energy storage converter is not more than 5s. Therefore, the safety voltage of the DC capacitor 31 can be set to 60V, and the expected discharge time of the energy storage converter can be set to 5s.

[0096] S430 : Determine a modulation wave signal according to the expected discharge time, the stored capacity of the DC capacitor, and the safety voltage of the DC capacitor.

[0097] Specifically, after the energy storage converter 3 stops working, the amount of electricity that the energy storage converter 3 needs to discharge can be calculated based on the real-time detected storage capacity of the DC capacitor and the safety voltage of the DC capacitor 31, and then combined with the expected discharge time, the discharge power that meets the discharge requirements of the energy storage converter 3 is obtained, thereby determining the amplitude and frequency of the modulation wave signal based on the discharge power. For example, a discharge power-modulation wave signal correspondence table can be pre-set. When the discharge power that meets the discharge requirements of the energy storage converter 3 is obtained, the amplitude and frequency of the modulation wave signal required at this time are queried by looking up the table. The discharge power can be positively correlated with the amplitude of the modulation wave signal. The greater the required discharge power, the higher the required discharge efficiency of the DC capacitor 31. The greater the amplitude of the modulation wave signal, the more intense the discharge process. The discharge power and the frequency of the modulation wave signal are positively correlated. The greater the required discharge power, the higher the required discharge efficiency of the DC capacitor 31. The greater the frequency of the modulation wave signal, the higher the frequency of repeated power transfer between the DC side and the AC side of the energy storage converter 3, and the greater the frequency of losses in the switching devices and the filter inductor 332 and the filter capacitor 331. It should be noted that when calibrating the discharge power-modulation wave signal correspondence table, it is necessary to ensure that the regulating effect of the modulation wave signal on the energy storage converter 3 does not exceed the rated capacity of the inverter 32 and related power electronic equipment to avoid damage to the components of the entire energy storage converter system.

[0098] S440 , generating a switch driving signal according to the modulation wave signal to control the on / off state of each switch in the inverter.

[0099] This embodiment determines the modulation wave signal by the expected discharge time, the stored capacity of the DC capacitor, and the safe voltage of the DC capacitor, so as to accurately adjust the modulation wave signal to control the output voltage of the inverter, thereby realizing discharge control of the energy storage converter and improving the accuracy and efficiency of discharge.

[0100] Example 6

[0101] Based on the above embodiments, Figure 6 This is a flow chart of another discharge method of an energy storage converter provided by an embodiment of the present invention. Figure 6 The discharge method of the energy storage converter shown in the figure explains how to control the on-off state of the switch in the inverter. Figure 1 and Figure 6 As shown, the discharging method of the energy storage converter also includes:

[0102] S510: When the energy storage converter stops working, a modulation wave signal is obtained.

[0103] S520 , determining three-phase modulation waves respectively according to the modulation wave signal.

[0104] Specifically, after obtaining the modulated wave signal, the modulated wave signal includes at least the modulated wave amplitude and the modulated wave phase, and then the modulated wave signal can be transformed by the DQ / ABC converter to generate a three-phase modulated wave. Exemplarily, the amplitude of the initial modulated wave signal corresponds to the "B" in the BQ conversion, and the amplitude control parameter "Q" is obtained by looking up the table or calculating. When the amplitude is 0.8, the BQ conversion table shows that Q = 0.75. Then, the modulated wave phase is used as the phase θ1 of the A-phase modulated wave, and the phases of the B-phase and C-phase modulated waves are determined according to the ABC conversion rule, that is, the B-phase signal phase θ2 = θ1-120°, and the C-phase signal phase θ3 = θ2-120°. Finally, based on the determined amplitude control parameter "Q" and the phase relationship of each phase signal, a three-phase modulated wave is generated.

[0105] Optional, Figure 7 : is a waveform diagram of a three-phase modulation wave provided by an embodiment of the present invention, such as Figure 1 and Figure 7 As shown, the stage in which the DC capacitor 31 is discharged through the inverter 32 includes a first moment t1 and a second moment t2, and the second moment t2 is located after the first moment t1; the amplitude of the modulated wave at the first moment t1 is the first amplitude, and the amplitude of the modulated wave at the second moment t2 is the second amplitude; the second amplitude is greater than the first amplitude; and / or, the stage in which the filter capacitor 331 is discharged through the inverter 32 includes a third moment t3 and a fourth moment t4, and the fourth moment t4 is located after the third moment t3; the amplitude of the modulated wave at the third moment t3 is the third amplitude, and the amplitude of the modulated wave at the fourth moment t4 is the fourth amplitude; the third amplitude is greater than the fourth amplitude.

[0106] Specifically, the three-phase modulated wave includes an A-phase modulated wave, a B-phase modulated wave, and a C-phase modulated wave. These three waves have the same amplitude (i.e., the modulated wave amplitude) during the primary discharge process of DC capacitor 31 or the discharge process of filter capacitor 331, and maintain a fixed phase difference between them. Inverter 32 can be considered a voltage source inverter circuit, whose output voltage is modulated by the DC capacitor 31 voltage through the switching action of inverter 331. The modulated wave is used to control the drive signal of the power switching device in inverter 32. When the amplitude of the modulated wave increases, the conduction time of the switching device in inverter 32 is prolonged, allowing the output end of inverter 32 to more fully obtain electrical energy from the DC side, ultimately resulting in an increase in the output voltage of inverter 32; and vice versa. Based on this, the process of discharging the DC capacitor 31 through the inverter 32 can be between the first moment t1 and the second moment t2. At the first moment t1, the amplitude of the modulation wave is a lower first amplitude. Since the circuit will tend to a steady state over time, the voltage of the filter capacitor 331 is equal to the output voltage of the DC capacitor 31 corresponding to the first amplitude modulation wave through the inverter 32, that is, the voltage of the filter capacitor 331 is relatively small at this time; as time passes to the second moment t2, the amplitude of the modulation wave increases to a higher second amplitude. Due to the increase in the amplitude of the modulation wave, the amplitude of the output voltage of the inverter 32 also increases, which makes the voltage across the DC capacitor 31 greater than the voltage of the filter capacitor 331, thereby generating a voltage difference between the DC capacitor 31 and the filter capacitor 331, resulting in a current from left to right on the filter inductor 332, thereby realizing the discharge process of the DC capacitor 31 to the filter capacitor 331 through the inverter 32.

[0107] It should be noted that the above description is merely an example of the process of the DC capacitor 31 discharging through the inverter 32 including the first moment and the second moment. The first moment and the second moment may be any two moments in the discharge process.

[0108] Correspondingly, the process of discharging the filter capacitor 331 through the inverter 32 can be between the second moment t3 and the fourth moment t4. At the third moment t3, the amplitude of the modulation wave is a higher third amplitude. Since the circuit tends to a steady state over time, the voltage of the filter capacitor 331 is equal to the output voltage of the DC capacitor 31 corresponding to the third amplitude modulation wave through the inverter 32, that is, the voltage of the filter capacitor 331 is larger at this time; as time passes to the fourth moment t4, the amplitude of the modulation wave decreases to a lower fourth amplitude. Due to the decrease in the amplitude of the modulation wave, the amplitude of the output voltage of the inverter 32 also decreases, which makes the voltage across the DC capacitor 31 less than the voltage of the filter capacitor 331, thereby generating a voltage difference between the DC capacitor 31 and the filter capacitor 331, resulting in a current from right to left on the filter inductor 332, thereby realizing the discharge process of the filter capacitor 331 to the DC capacitor 331 through the inverter 32.

[0109] It should be noted that the above description is merely an example of the process of the filter capacitor 331 discharging through the inverter 32 including the third moment and the fourth moment. The third moment and the fourth moment may be any two moments in the discharge process.

[0110] Furthermore, by periodically changing the amplitude of the modulation wave, the output voltage of the inverter 32 can be controlled, and then the effective discharge of the DC capacitor 31 to the filter capacitor 331 and the effective discharge of the filter capacitor 331 to the DC capacitor 31 can be periodically controlled, so as to realize the alternating transmission of power from the DC side to the AC side of the energy storage converter 3 and the transmission from the AC side to the DC side. The repeated transmission causes the residual energy on the DC capacitor 31 to be repeatedly lost in the switching device, the filter capacitor 331 and the filter inductor 332, thereby dissipating the energy stored in the DC bus capacitor and achieving the purpose of active discharge of the energy storage converter 3.

[0111] Optional, Figure 8 This is another waveform diagram of a three-phase modulation wave provided by an embodiment of the present invention, such as Figure 1 and Figure 8 As shown, the stage in which the DC capacitor is discharged through the inverter also includes a fifth moment t5, the fifth moment t5 is located after the second moment t2, the interval between the first moment t1 and the second moment t2 is equal to the interval between the second moment t2 and the fifth moment t5; at the fifth moment t5, the amplitude of the modulated wave is the fifth amplitude; the fifth amplitude is greater than the second amplitude; the difference between the first amplitude and the second amplitude is equal to the difference between the second amplitude and the fifth amplitude; and / or, the stage in which the filter capacitor is discharged through the inverter also includes a sixth moment t6, the sixth moment t6 is located after the fourth moment t4, the interval between the third moment t3 and the fourth moment t4 is equal to the interval between the fourth moment t4 and the sixth moment t6; at the sixth moment t6, the amplitude of the modulated wave is the sixth amplitude; the fourth amplitude is greater than the sixth amplitude; and the difference between the third amplitude and the fourth amplitude is equal to the difference between the fourth amplitude and the sixth amplitude.

[0112] Specifically, the three-phase modulated wave includes an A-phase modulated wave, a B-phase modulated wave, and a C-phase modulated wave. The amplitudes of these three waves (i.e., the modulated wave amplitudes) vary continuously over time during the primary discharge process of DC capacitor 31 or the discharge process of filter capacitor 331, and maintain a fixed phase difference between them. Inverter 32 can be considered a voltage source inverter circuit, whose output voltage is modulated by the DC capacitor 31 voltage through the switching action of inverter 331. The modulated wave is used to control the drive signal of the power switching devices in inverter 32. When the amplitude of the modulated wave increases, the conduction time of the switching devices in inverter 32 is prolonged, allowing the output end of inverter 32 to more fully obtain electrical energy from the DC side, ultimately resulting in an increase in the output voltage of inverter 32; and vice versa. Based on this, the process of discharging the DC capacitor 31 through the inverter 32 can be between the first moment t1 and the second moment t2 and between the second moment t2 and the fifth moment t5. At the first moment t1, the amplitude of the modulation wave is a lower first amplitude. Since the circuit tends to a steady state over time, the voltage of the filter capacitor 331 is equal to the output voltage of the DC capacitor 31 corresponding to the first amplitude modulation wave through the inverter 32, that is, the voltage of the filter capacitor 331 is relatively small at this time; as time passes to the second moment t2, the amplitude of the modulation wave increases to a higher second amplitude. Due to the increase in the amplitude of the modulation wave, the amplitude of the output voltage of the inverter 32 also increases, which makes the voltage across the DC capacitor 31 greater than the voltage of the filter capacitor 331, thereby generating a voltage difference between the DC capacitor 31 and the filter capacitor 331, resulting in a current from left to right on the filter inductor 332, thereby realizing the discharge process of the DC capacitor 31 to the filter capacitor 331 through the inverter 32. The fifth moment t5 is located after the second moment t2, and the interval between the fifth moment t5 and the second moment t2 is equal to the interval between the first moment t1 and the second moment t2. The modulation wave amplitude corresponding to the fifth moment t5 is the fifth amplitude, the fifth amplitude is greater than the second amplitude, and the difference between the first amplitude and the second amplitude is equal to the difference between the second amplitude and the fifth amplitude. The principle of the discharge process of the DC capacitor 31 to the filter capacitor 331 through the inverter 32 between the second moment t2 and the fifth moment t5 is the same as the principle of the discharge process of the DC capacitor 31 to the filter capacitor 331 through the inverter 32 between the first moment t1 and the second moment t2, and will not be repeated here.

[0113] It should be noted that the above description is merely an example of the process of discharging the DC capacitor 31 through the inverter 32 including the first moment, the second moment and the fifth moment. The first moment, the second moment and the fifth moment may be any three moments in the discharge process.

[0114] Correspondingly, the process of discharging the filter capacitor 331 through the inverter 32 can be between the second moment t3 and the fourth moment t4. At the third moment t3, the amplitude of the modulation wave is a higher third amplitude. Since the circuit tends to a steady state over time, the voltage of the filter capacitor 331 is equal to the output voltage of the DC capacitor 31 corresponding to the third amplitude modulation wave through the inverter 32, that is, the voltage of the filter capacitor 331 is larger at this time; as time passes to the fourth moment t4, the amplitude of the modulation wave decreases to a lower fourth amplitude. Due to the decrease in the amplitude of the modulation wave, the amplitude of the output voltage of the inverter 32 also decreases, which makes the voltage across the DC capacitor 31 less than the voltage of the filter capacitor 331, thereby generating a voltage difference between the DC capacitor 31 and the filter capacitor 331, resulting in a current from right to left on the filter inductor 332, thereby realizing the discharge process of the filter capacitor 331 to the DC capacitor 331 through the inverter 32. The sixth moment t6 is located after the fourth moment t4, and the interval between the sixth moment t6 and the fourth moment t4 is equal to the interval between the third moment t3 and the fourth moment t4. The modulated wave amplitude corresponding to the sixth moment t6 is the sixth amplitude, the sixth amplitude is greater than the fourth amplitude, and the difference between the third amplitude and the fourth amplitude is equal to the difference between the fourth amplitude and the sixth amplitude. The principle of the discharge process of the filter capacitor 331 to the DC capacitor 31 through the inverter 32 between the fourth moment t4 and the sixth moment t6 is the same as the principle of the discharge process of the filter capacitor 331 to the DC capacitor 31 through the inverter 32 between the third moment t3 and the fourth moment t4, and will not be repeated here.

[0115] It should be noted that the above description is merely an example of the process of discharging the filter capacitor 331 through the inverter 32 including the third moment, the fourth moment and the sixth moment. The third moment, the fourth moment and the sixth moment may be any three moments in the discharge process.

[0116] Furthermore, by periodically changing the amplitude of the modulation wave, the output voltage of the inverter 32 can be controlled, and then the effective discharge of the DC capacitor 31 to the filter capacitor 331 and the effective discharge of the filter capacitor 331 to the DC capacitor 31 can be periodically controlled, so as to realize the alternating transmission of power from the DC side to the AC side of the energy storage converter 3 and the transmission from the AC side to the DC side. The repeated transmission causes the residual energy on the DC capacitor 31 to be repeatedly lost in the switching device, the filter capacitor 331 and the filter inductor 332, thereby dissipating the energy stored in the DC bus capacitor and achieving the purpose of active discharge of the energy storage converter 3.

[0117] It is understandable that, at intervals of the same time period, the amplitude of the modulated wave continuously increases or decreases at a fixed value over time, which can make the change in the output voltage of the inverter 32 more stable, reduce the impact on the equipment, and thus improve the stability and reliability of the entire system. On the other hand, the proportional change in the amplitude of the modulated wave with time causes the output voltage of the inverter 32 to be constantly changing (increasing or decreasing), forcing a constant voltage difference between the DC capacitor 31 and the filter capacitor 331, preventing it from reaching a steady state. As a result, there is always current in the circuit to consume the residual energy of the energy storage converter 3 through the switching device, filter inductor 332 and filter capacitor 331, thereby improving the discharge efficiency of the energy storage converter 3.

[0118] S530 : Determine a switch driving signal according to the three-phase modulation wave to control the on / off state of each switch in the inverter.

[0119] Specifically, based on the generated three-phase modulated wave, the drive signal for the switching tube of inverter 32 can be determined through pulse width modulation (PWM) technology. First, the three-phase modulated wave is compared with a high-frequency triangular carrier (such as 10kHz) to generate a corresponding PWM waveform. When the amplitude of the modulated wave is higher than the carrier, the upper tube of the corresponding bridge arm is driven to turn on and the lower tube is driven to turn off. Conversely, the lower tube is driven to turn on and the upper tube is driven to turn off. By adjusting the amplitude and frequency of the modulated wave, the duty cycle and switching timing of the switching tube can be dynamically controlled, thereby accurately adjusting the equivalent voltage and current path of the inverter output, and realizing the rapid discharge of DC capacitor energy through the filter inductor 332 and the switching tube.

[0120] This embodiment determines a three-phase modulation wave through the amplitude and phase of the modulation wave signal, and determines a switch drive signal through the three-phase modulation wave to control the on-off state of each switch in the inverter. The original hardware of the inverter is reused to consume the residual energy of the DC capacitor without the need for an external circuit, making the discharge process of the energy storage inverter both efficient and safe.

[0121] Example 7

[0122] Based on the above embodiments, Figure 9 This is a flow chart of another discharge method of an energy storage converter provided by an embodiment of the present invention. Figure 9 The discharging method of the energy storage converter shown in the figure explains when to stop discharging the energy storage converter. Figure 1 and Figure 9 As shown, the discharging method of the energy storage converter includes:

[0123] S610: When the energy storage converter stops working, obtain a modulation wave signal.

[0124] S620: Before the DC capacitor is discharged through the switches of the inverter, obtain the current voltage between the two substrates of the DC capacitor.

[0125] S630: When the current voltage is less than or equal to the preset threshold, stop generating the switch driving signal.

[0126] S640: When the current voltage is greater than a preset threshold, generate a switch drive signal according to the modulation wave signal to control the on / off state of each switch in the inverter.

[0127] Specifically, the DC capacitor 31 has certain withstand voltage and capacity specifications. If it is over-discharged, it may damage the capacitor, shorten its service life, and even cause safety hazards such as leakage, swelling, explosion, etc. Therefore, in order to prevent over-discharge, before the DC power 31 is discharged through the inverter 32, the current voltage of the DC capacitor 31 can be obtained by a voltage sensor and compared with a preset threshold. If the current voltage of the DC capacitor 31 is less than or equal to the preset threshold, the generation of the switch drive signal is immediately terminated, and the conduction state of all switch tubes is forced to be turned off; if the current voltage of the DC capacitor 31 is greater than the preset threshold, it means that the DC capacitor 31 has not dropped to a safe voltage. Then, a switch drive signal is generated according to the modulated wave signal to control the on-off state of each switch in the inverter, thereby realizing the discharge process of the energy storage converter 3. This voltage closed-loop protection mechanism ensures that the discharge process automatically stops after reaching a safe voltage, avoiding the risk of electrolyte decomposition or low-voltage reverse charging caused by capacitor over-discharge, protecting the safety and performance of the DC capacitor 31, and providing safety protection for operation and maintenance personnel. For example, the preset threshold can be 60V.

[0128] In this embodiment, before the DC capacitor is discharged through each switch of the inverter, the current voltage between the two substrates of the DC capacitor is obtained to determine whether the DC capacitor currently needs to be discharged. The timing and degree of discharge can be accurately adjusted according to actual needs, providing safety protection for operation and maintenance personnel while extending the service life of the energy storage inverter and preventing damage to the energy storage inverter due to excessive discharge.

[0129] Example 8

[0130] Based on the same inventive concept, Figure 10 FIG. 1 is a structural diagram of a discharge device of an energy storage converter provided by an embodiment of the present invention. Figure 1 and Figure 10 As shown, a discharge device of an energy storage converter provided in this embodiment includes: an acquisition module 710 and a control module 720;

[0131] An acquisition module 710 is configured to acquire a modulation wave signal when the energy storage converter stops working;

[0132] The control module 720 is used to generate a switch drive signal according to the modulation wave signal to control the on-off state of each switch in the inverter; wherein, when controlling the on-off state of the switch in the inverter, the DC capacitor is discharged through the inverter, or the filter capacitor is discharged through the inverter.

[0133] Specifically, the acquisition module 710 is connected to the control module 720, and the DC capacitor 31 continuously performs a charge and discharge cycle during the operation of the energy storage converter 3. Under normal operating conditions, the DC capacitor 31 continuously absorbs and releases energy according to the working mode (charging or discharging) and power demand of the energy storage converter 3. However, the charging and discharging process of the DC capacitor 31 is not completed instantly, but there is a certain time constant. Before the energy storage converter 3 stops working due to a shutdown instruction, fault protection or grid abnormality, the DC capacitor 31 may have obtained a certain amount of energy from the grid or other power supply, and suddenly interrupted in the process of providing energy to the load. At this time, although the energy storage converter 3 stops working, the charge distribution inside the DC capacitor 31 cannot change immediately. The energy stored in the DC capacitor 31 does not have time to be completely released, and the voltage across it will not immediately return to zero, so that the DC capacitor 31 itself is still in a charged state and has residual energy. After the energy storage converter 3 stops working, the on and off states of the switch of the inverter 32 in the energy storage converter 3 can be controlled by pulse width modulation, and the residual energy of the DC capacitor 31 is used to generate a three-phase AC voltage on the filter capacitor 331. The three-phase AC voltage can be in the shape of a sine wave.

[0134] Furthermore, according to the actual situation of the energy storage converter 3, a modulation wave signal corresponding to the real-time situation at this moment and capable of discharging the DC capacitor 31 is obtained from the outside through the acquisition module 710. The modulation wave signal is a reference waveform used to control the on and off of switching devices in the power electronic system. The voltage or current characteristics output by the inverter 32 are controlled by adjusting its parameters. The parameters of the modulation wave signal include at least the modulation wave amplitude and the modulation wave phase, wherein the modulation wave amplitude is positively correlated with the amplitude of the output voltage of the inverter 32, and the modulation wave phase is the same as the phase of the output voltage of the inverter 32.

[0135] Accordingly, the control module 720 receives the modulated wave signal transmitted by the acquisition module 710. The modulated wave signal can be a signal with certain frequency, amplitude, and phase characteristics. The control module 720 uses a specific modulation technique (such as pulse width modulation (PWM) or sinusoidal pulse width modulation (SPWM)) to compare the modulated wave signal with a carrier signal (typically a triangular wave or sawtooth wave) in real time. When the amplitude of the modulated wave signal is greater than the carrier signal, a high-level switch drive signal is generated; when the amplitude of the modulated wave signal is less than the carrier signal, a low-level switch drive signal is generated. These high and low-level switch drive signals generated by the control module 720 serve as reference signals in the inverter control and are used to control the on and off of various switching devices (such as IGBTs, MOSFETs, etc.) in the inverter 32. For example, if the inverter 32 is a three-phase bridge inverter, when the switch drive signal is high, the switch transistors in the upper bridge arm can be turned on and the switch transistors in the lower bridge arm can be turned off; when the switch drive signal is low, the switch transistors in the upper bridge arm can be turned off and the switch transistors in the lower bridge arm can be turned on.

[0136] Furthermore, after the residual energy of the DC capacitor 31 generates a three-phase AC voltage on the filter capacitor 331 for a period of time, the circuit characteristics will naturally converge to a steady state, that is, the output voltage V1 of the DC capacitor 31 through the inverter 32 is the same as the voltage V2 of the filter capacitor 331. At this time, if the switch drive signal generated by the control module 720 controls the conduction state of each switch in the inverter 32, so that the output voltage V1 of the DC capacitor 31 through the inverter 32 increases, V1>V2, and then a current from left to right will be generated on the filter inductor 332, and the DC capacitor 31 discharges the filter capacitor 331 through the inverter 32, combined with the damping effect of the parasitic resistance in the circuit, until the voltage V2 of the filter capacitor 331 rises to be equal to the output voltage V1 of the DC capacitor 31 through the inverter 32 again, thereby entering a new steady state. State; If the switch drive signal generated by the control module 720 controls the conduction state of each switch in the inverter 32, so that the output voltage V1 of the DC capacitor 31 through the inverter 32 decreases, V1 < V2, and then a current from right to left is generated on the filter inductor 332, the filter capacitor 331 discharges the DC capacitor 31 through the inverter 32, combined with the damping effect of the parasitic resistance in the circuit, until the voltage V2 of the filter capacitor 331 decreases to equal the output voltage V1 of the DC capacitor 31 through the inverter 32 again, thus entering a new steady state. Based on this, the control module 720 periodically applies the above two switch drive signals to the inverter 32, thereby controlling the conduction state of each switch in the inverter 32 to alternately change, so as to achieve repeated power transfer between the DC side and the AC side of the energy storage converter 3. Since each transfer will generate losses in the switch devices and the filter capacitor 331 and the filter inductor 332, the repeated power transfer will generate repeated losses, thereby dissipating the residual energy on the DC capacitor 31 and achieving the purpose of active discharge.

[0137] The discharge device of the energy storage converter provided in the embodiment of the present invention can execute the discharge method of the energy storage converter provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

[0138] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0139] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A discharge method for an energy storage converter, characterized in that: The energy storage converter includes a DC capacitor, an inverter and a filter; wherein the DC capacitor is connected in parallel to the DC side of the inverter, the filter is electrically connected to the AC side of the inverter, and the filter includes a filter capacitor; The discharging method of the energy storage converter includes: When the energy storage converter stops working, obtaining a modulation wave signal; A switch drive signal is generated according to the modulated wave signal to control the on / off state of each switch in the inverter; wherein, when controlling the on / off state of the switches in the inverter, the DC capacitor is discharged through the inverter, or the filter capacitor is discharged through the inverter.

2. The discharging method of the energy storage converter according to claim 1, characterized in that: The discharge method further comprises: Acquiring the three-phase voltage on the AC side of the inverter in real time; The modulated wave signal is adjusted according to the three-phase voltage on the AC side.

3. The discharging method of the energy storage converter according to claim 1, characterized in that: Before obtaining the modulated wave signal, it also includes: Obtaining status information of the energy storage converter; wherein the DC side of the inverter is further provided with a DC contactor, and the AC side of the inverter is further provided with an AC contactor; the status information includes the on-off state of the DC contactor, the on-off state of the AC contactor, the voltage on the DC side of the inverter, and the voltage on the AC side of the inverter; When the status information meets the preset conditions, it is determined that the energy storage converter stops working; wherein the preset conditions include that the DC contactor and the AC contactor are both in the disconnected state, and the voltage on the DC side is less than the preset DC voltage, and the voltage on the AC side is less than the preset AC voltage.

4. The discharging method of the energy storage converter according to claim 1, characterized in that: Also includes: Obtaining an expected discharge time of the energy storage converter, a stored amount of electricity of the DC capacitor, and a safety voltage of the DC capacitor; The modulation wave signal is determined according to the expected discharge time, the stored electricity of the DC capacitor, and the safety voltage of the DC capacitor.

5. The discharging method of the energy storage converter according to claim 1, characterized in that: Generating a switch drive signal according to the modulated wave signal to control the on / off state of each switch in the inverter includes: Determining three-phase modulation waves respectively according to the modulation wave signals; The switch driving signal is determined according to the three-phase modulation wave to control the on-off state of each switch in the inverter.

6. The discharging method of the energy storage converter according to claim 1, characterized in that: The stage in which the DC capacitor is discharged through the inverter includes a first moment and a second moment, the second moment being located after the first moment; the amplitude of the modulated wave at the first moment is a first amplitude, and the amplitude of the modulated wave at the second moment is a second amplitude; the second amplitude is greater than the first amplitude; and / or, The stage in which the filter capacitor is discharged through the inverter includes a third moment and a fourth moment, and the fourth moment is located after the third moment; at the third moment, the amplitude of the modulated wave is the third amplitude, and at the fourth moment, the amplitude of the modulated wave is the fourth amplitude; the third amplitude is greater than the fourth amplitude.

7. The discharging method of the energy storage converter according to claim 6, characterized in that: The stage in which the DC capacitor is discharged through the inverter further includes a fifth moment, the fifth moment being located after the second moment, and the interval between the first moment and the second moment being equal to the interval between the second moment and the fifth moment; At the fifth moment, the amplitude of the modulated wave is a fifth amplitude; the fifth amplitude is greater than the second amplitude; The difference between the first amplitude and the second amplitude is equal to the difference between the second amplitude and the fifth amplitude; and / or, The stage in which the filter capacitor discharges through the inverter also includes a sixth moment, the sixth moment is located after the fourth moment, the interval between the third moment and the fourth moment is equal to the interval between the fourth moment and the sixth moment; at the sixth moment, the amplitude of the modulated wave is the sixth amplitude; the fourth amplitude is greater than the sixth amplitude; the difference between the third amplitude and the fourth amplitude is equal to the difference between the fourth amplitude and the sixth amplitude.

8. The discharging method of the energy storage converter according to claim 1, characterized in that: Also includes: Before the DC capacitor is discharged through each of the switches of the inverter, obtaining a current voltage between two substrates of the DC capacitor; When the current voltage is less than or equal to a preset threshold, the switch driving signal is stopped from being generated.

9. A discharge device for an energy storage converter, characterized in that: The energy storage converter includes a DC capacitor, an inverter and a filter; wherein the DC capacitor is connected in parallel to the DC side of the inverter, the filter is electrically connected to the AC side of the inverter, and the filter includes a filter capacitor; The discharging device of the energy storage converter includes: an acquisition module and a control module; The acquisition module is used to acquire the modulation wave signal when the energy storage converter stops working; The control module is used to generate a switch drive signal according to the modulated wave signal to control the on-off state of each switch in the inverter; wherein, when controlling the on-off state of the switch in the inverter, the DC capacitor is discharged through the inverter, or the filter capacitor is discharged through the inverter.

10. An energy storage converter, characterized in that: include: Controllers, DC capacitors, inverters, and filters; The controller is connected to the inverter, the DC capacitor is connected in parallel to the DC side of the inverter, the filter is electrically connected to the AC side of the inverter, and the filter includes a filter capacitor; The controller is used to execute the discharging method of the energy storage converter according to any one of claims 1 to 8.

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