Current control system, current control method and device of inverter

Abstract

The application provides a current control system, a current control method and a device thereof. The current control system comprises a controller configured to obtain a first driving voltage of an inverter according to a reference voltage parameter of the inverter; the reference voltage parameter of the inverter is determined according to a reference power of the inverter, an actual output power of the inverter and a mapping relationship between the power and the voltage parameter; the controller is further configured to determine a second driving voltage of the inverter according to the first driving voltage and a damping voltage of the inverter; the damping voltage of the inverter is determined according to a virtual impedance value of the inverter and a current output of the inverter; and the controller is further configured to generate a driving signal according to the second driving voltage and send the driving signal to the inverter, wherein the driving signal is used to control the current output of the inverter. The application can control the current output of the inverter.

Description

Technical Field

[0001] This application relates to the field of power supply technology, and in particular to a current control system, current control method and device for an inverter. Background Technology

[0002] Inverters convert direct current (DC) to alternating current (AC) and are widely used in power systems. Power systems require inverters to have a certain low voltage ride-through (LVRT) capability. In other words, inverters need to have a certain current withstand and current limiting capability so that even if a power system fault occurs, causing a voltage drop and an increase in current, the inverter can still operate normally and not be burned out.

[0003] An inverter contains multiple semiconductor devices, such as metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), and their anti-parallel diodes. Since semiconductor devices generally have low current handling capability, current research focuses on controlling the inverter's output current to ensure that the inverter's LVRT meets the requirements of the power system. Summary of the Invention

[0004] This application provides a current control system, current control method and device for an inverter, which can control the output current of the inverter.

[0005] In a first aspect, embodiments of this application provide a current control system for an inverter, which includes a DC power supply, an inverter, an AC load, and a controller, wherein the input terminal of the inverter is coupled to the DC power supply, the output terminal of the inverter is coupled to the AC load, and the control terminal of the inverter is coupled to the controller.

[0006] The controller is used to obtain the first drive voltage of the inverter based on the reference voltage parameter of the inverter; the reference voltage parameter of the inverter is determined based on the reference power of the inverter, the actual output power of the inverter, and the mapping relationship between power and voltage parameters;

[0007] The controller is also used to determine the second drive voltage of the inverter based on the first drive voltage and the damping voltage of the inverter; the damping voltage of the inverter is determined based on the virtual impedance value of the inverter and the current output current of the inverter.

[0008] The controller is also used to generate a drive signal based on the second drive voltage and send the drive signal to the inverter, the drive signal being used to control the output current of the inverter.

[0009] In this embodiment, the controller determines the damping voltage by comparing the inverter's current output current with the virtual impedance value. This damping voltage is then subtracted from the first drive voltage to obtain the second drive voltage, which is used to generate a drive signal. By implementing this embodiment, the damping voltage can directly change the inverter's drive voltage, thereby generating a new drive signal and controlling the inverter's output current.

[0010] In conjunction with the first aspect, in a first possible implementation, the controller is further configured to determine the reference power of the inverter based on the output voltage of the inverter, the rated voltage of the inverter, and the preset power of the inverter.

[0011] The embodiments of this application add the determination of reference power, so that when the output voltage of the inverter is lower than the preset voltage threshold, the controller can not only increase the damping voltage to change the drive voltage of the inverter, but also further control the reference power of the inverter, thereby controlling the output current of the inverter.

[0012] In conjunction with the first aspect or the first possible implementation of the first aspect, in the second possible implementation, the aforementioned reference power includes reference active power and reference reactive power, and the aforementioned actual output power includes actual active power and actual reactive power.

[0013] The aforementioned reference voltage parameters include reference voltage amplitude and reference voltage frequency; the mapping relationship between the aforementioned power and voltage reference parameters includes the mapping relationship between active power and voltage frequency and the mapping relationship between reactive power and voltage amplitude;

[0014] The controller is further configured to determine the reference voltage frequency of the inverter based on the reference active power, the actual active power, and the mapping relationship between the active power and the voltage frequency.

[0015] The controller is further configured to determine the reference voltage amplitude of the inverter based on the reference reactive power, the actual reactive power, and the mapping relationship between the reactive power and the voltage amplitude.

[0016] In conjunction with the second possible implementation of the first aspect, in the third possible implementation, the aforementioned preset power includes preset reactive power and rated apparent power;

[0017] The controller is also used to determine the reference reactive power of the inverter based on the output voltage of the inverter, the rated voltage of the inverter, and the preset reactive power.

[0018] The controller is also configured to determine the reference active power of the inverter based on the reference reactive power of the inverter, the output voltage of the inverter, the rated voltage of the inverter, and the rated apparent power of the inverter.

[0019] In a fourth possible implementation, in conjunction with the first aspect or any of the above possible implementations, the controller is further configured to determine the reference current of the inverter based on the reference voltage parameter of the inverter and the output voltage of the inverter.

[0020] The controller is further configured to determine the first drive voltage of the inverter based on the reference current of the inverter and the current output current of the inverter.

[0021] In this embodiment, the damping voltage is directly calculated with the first driving voltage, and the inverter's current control system responds effectively and quickly.

[0022] In a fifth possible implementation, in conjunction with the first aspect or any of the above possible implementations of the first aspect, the controller is further configured to determine the virtual impedance value based on the difference between the current output current of the inverter and the first preset current threshold and the first preset impedance value.

[0023] In implementing the embodiments of this application, the virtual impedance value changes with the magnitude of the inverter's output current, making the inverter's second drive voltage more accurate and adaptable.

[0024] In a sixth possible implementation, in combination with the first aspect or any one of the first to fourth possible implementations of the first aspect, the inverter includes a three-phase inverter.

[0025] The controller described above is used to determine the corresponding second drive voltage of each phase in the three-phase inverter based on the first drive voltage of each phase and the corresponding damping voltage of each phase; wherein the corresponding damping voltage of each phase in the three-phase inverter is determined based on the virtual impedance value of each phase in the three-phase inverter and the corresponding output current of each phase in the three-phase inverter.

[0026] The controller is further configured to generate each drive signal according to the corresponding second drive voltage in the three-phase inverter, and send the corresponding drive signal to each phase of the three-phase inverter respectively. Each drive signal is used to control the output current of each phase in the three-phase inverter.

[0027] By implementing the embodiments of this application, the output current of each phase of the inverter can be judged independently, and the virtual impedance value of each phase of the inverter can be calculated separately. The results obtained are more accurate and applicable to scenarios where misalignment faults occur in each phase of the inverter, making it more versatile.

[0028] In conjunction with the sixth possible implementation of the first aspect, in the seventh possible implementation, the controller is further configured to determine the virtual impedance value of each phase of the three-phase inverter based on the difference between the output current of each phase of the three-phase inverter and the corresponding second preset current threshold of each phase of the three-phase inverter, as well as the second preset impedance value.

[0029] In any of the first to seventh possible implementations of the first aspect, in the eighth possible implementation, the output voltage of the inverter is lower than a preset voltage threshold.

[0030] Secondly, embodiments of this application provide a current control method for an inverter, wherein the input terminal of the inverter is coupled to a DC power supply, the output terminal of the inverter is coupled to an AC load, and the control terminal of the inverter is coupled to a current controller. The current control method is applicable to the controller and includes:

[0031] The first drive voltage of the inverter is obtained based on the reference voltage parameters of the inverter mentioned above; the reference voltage parameters of the inverter are determined based on the reference power of the inverter, the actual output power of the inverter, and the mapping relationship between power and voltage parameters;

[0032] The second drive voltage of the inverter is determined based on the first drive voltage and the damping voltage of the inverter; the damping voltage of the inverter is determined based on the virtual impedance value of the inverter and the current output current of the inverter.

[0033] A drive signal is generated based on the second drive voltage and sent to the inverter. The drive signal is used to control the output current of the inverter.

[0034] In conjunction with the second aspect, in the first possible implementation, the reference power of the inverter is determined based on the inverter's output voltage, the inverter's rated voltage, and the inverter's preset power.

[0035] In conjunction with the second aspect or the first possible implementation of the second aspect, in the second possible implementation, the aforementioned reference power includes reference active power and reference reactive power, and the aforementioned actual output power includes actual active power and actual reactive power.

[0036] The aforementioned reference voltage parameters include reference voltage amplitude and reference voltage frequency; the mapping relationship between the aforementioned power and voltage reference parameters includes the mapping relationship between active power and voltage frequency and the mapping relationship between reactive power and voltage amplitude;

[0037] The reference voltage frequency of the inverter is determined based on the reference active power, the actual active power, and the mapping relationship between the active power and the voltage frequency.

[0038] The reference voltage amplitude of the inverter is determined based on the reference reactive power, the actual reactive power, and the mapping relationship between the reactive power and the voltage amplitude.

[0039] In conjunction with the second possible implementation of the second aspect, in the third possible implementation, the aforementioned preset power includes preset reactive power and rated apparent power;

[0040] The reference reactive power of the inverter is determined based on the inverter's output voltage, rated voltage, and preset reactive power.

[0041] The reference active power of the inverter is determined based on the reference reactive power of the inverter, the output voltage of the inverter, the rated voltage of the inverter, and the rated apparent power.

[0042] In a fourth possible implementation, combining the second aspect or any of the above possible implementations of the second aspect,

[0043] The specific implementation of obtaining the first drive voltage of the inverter based on the inverter's reference voltage parameter is as follows:

[0044] Based on the reference voltage parameters and output voltage of the inverter, determine the reference current of the inverter.

[0045] The first drive voltage of the inverter is determined based on the reference current of the inverter and the current output current of the inverter.

[0046] In a fifth possible implementation, in conjunction with the second aspect or any of the above possible implementations of the second aspect, the virtual impedance value is determined based on the difference between the current output current of the inverter and the first preset current threshold and the first preset impedance value.

[0047] In a sixth possible implementation, in combination with the first aspect or any one of the first to fourth possible implementations of the first aspect, the inverter includes a three-phase inverter.

[0048] The determination of the second drive voltage of the inverter based on the first drive voltage and the damping voltage of the inverter includes:

[0049] Based on the first driving voltage of each phase in the three-phase inverter and the corresponding damping voltage, the corresponding second driving voltage of each phase in the three-phase inverter is determined; wherein the corresponding damping voltage of each phase in the three-phase inverter is determined based on the virtual impedance value of each phase in the three-phase inverter and the corresponding output current of each phase in the three-phase inverter.

[0050] The specific implementation of generating a drive signal based on the second drive voltage and sending the drive signal to the inverter is as follows:

[0051] Each drive signal is generated based on the corresponding second drive voltage in the three-phase inverter, and the corresponding drive signal is sent to each phase of the three-phase inverter. Each drive signal is used to control the output current of each phase of the three-phase inverter.

[0052] In conjunction with the sixth possible implementation of the second aspect, in the seventh possible implementation, the virtual impedance value of each phase in the three-phase inverter is determined based on the difference between the corresponding output current of each phase in the three-phase inverter and the corresponding second preset current threshold of each phase in the three-phase inverter, as well as the corresponding second preset impedance value.

[0053] In the eighth possible implementation, in combination with any one of the first to seventh possible implementations of the second aspect, the output voltage of the inverter is lower than a preset voltage threshold.

[0054] Thirdly, embodiments of this application provide a current controller for an inverter, the current controller including: a transceiver, a processor, and a memory, the transceiver, the processor, and the memory being coupled through a bus system;

[0055] This transceiver is used to receive the current output current and output voltage of the inverter, and to send drive signals to the inverter.

[0056] This memory is used to store instructions;

[0057] The processor is used to invoke instructions stored in the aforementioned memory to execute the second aspect described above, or to execute method steps in combination with any possible implementation of the second aspect described above.

[0058] It should be understood that the implementations and beneficial effects of the above-mentioned aspects of this application can be referenced from each other. Attached Figure Description

[0059] Figure 1AA structural block diagram of a current control system for a single-phase inverter provided in this application embodiment;

[0060] Figure 1B A structural block diagram of a current control system for a three-phase inverter provided in this application embodiment;

[0061] Figure 2 A structural block diagram of the current controller of an inverter provided in an embodiment of this application;

[0062] Figure 3A The droop characteristic curve between active power and voltage frequency is provided for the embodiments of this application;

[0063] Figure 3B The droop characteristic curve between reactive power and voltage amplitude provided in the embodiments of this application;

[0064] Figure 4 A schematic diagram illustrating the calculation of virtual impedance provided in an embodiment of this application;

[0065] Figure 5 Another schematic diagram illustrating the calculation of virtual impedance provided in the embodiments of this application;

[0066] Figure 6 Another structural block diagram of the current controller of the inverter provided in the embodiments of this application;

[0067] Figure 7 A schematic diagram illustrating the effect of implementing the embodiments of this application. Detailed Implementation

[0068] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0069] The following is combined Figures 1A to 5 The implementation of the embodiments of this application will be described in further detail below.

[0070] First see Figure 1A , Figure 1A This is a structural block diagram of a current control system for a single-phase inverter provided in an embodiment of this application. Figure 1A As shown, the current control system includes a DC power supply 100, an inverter 101a, an AC load 102, and a controller 103. The input terminal of the inverter 101a is coupled to the DC power supply 100, the output terminal of the inverter 101a is coupled to the AC load 102, and the control terminal of the inverter 101a is coupled to the controller 103.

[0071] It should be noted first that the "coupling" described in this application refers to a direct or indirect connection. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For example, A can be directly connected to C, and C can be directly connected to B, thus achieving a connection between A and B through C.

[0072] The DC power supply 100 is used to provide DC power to the inverter 101a, and can be a photovoltaic system, an electrochemical battery (such as a nickel-cadmium battery, a nickel-metal hydride battery, a lithium-ion battery, a lithium polymer battery, etc.) or a DC generator.

[0073] The inverter connects the DC power supply 100 to the AC load 102, converting the DC power provided by the DC power supply 100 into AC power and supplying that AC power to the AC load 102. For example, the inverter can be a single-phase inverter, such as... Figure 1A The inverter 101a shown includes four IGBTs, anti-parallel diodes, resistors, and inductors. The controller 103 can control the on / off state of each IGBT, enabling the inverter 101a to convert the DC power supplied by the DC power supply 100 into single-phase AC power. The AC load 102 can then be a single-phase AC load (i.e., a single-phase AC power grid), such as a transformer or a loudspeaker.

[0074] In some feasible implementations, the inverter can be a three-phase inverter. See also Figure 1B , Figure 1B This is a structural block diagram of a current control system for a three-phase inverter provided in an embodiment of this application. Figure 1B As shown, the current control system is also applicable to three-phase inverters. Figure 1B The current control system shown is Figure 1A The difference between the current control system shown in the diagram is that... Figure 1A The circuit topology of the inverter 101a is replaced with Figure 1B The inverter 101b is shown. This inverter 101b is a three-phase inverter. IGBTs and their anti-parallel diodes are connected in series in pairs to form one phase of the inverter 101b circuit. The three phases of the inverter 101b are connected in parallel. The controller 103 controls the on / off state of each IGBT in the inverter 101b, enabling the inverter 101b to convert the DC power supplied by the DC power supply 100 into three-phase AC power. At this time, the AC load 102 can be a three-phase AC load (i.e., a three-phase AC power grid), such as a three-phase motor.

[0075] Understandable, Figure 1A and Figure 1BThe inverters 101a and 101b shown are merely illustrative examples of inverter topologies and not exhaustive. It should be understood that the inverters of this application can also be implemented as other topologies, such as full-bridge inverters and half-bridge inverters in the prior art. This application does not limit the specific circuit structure of the inverter. In other words, the inverters involved in this application include, but are not limited to, those mentioned above. Figure 1A The inverter 101a shown in the figure and Figure 1B Inverter 101b is shown in the figure.

[0076] The controller 103 may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. For example, the input terminals of the controller 103 may be coupled to sensors such as voltage sensors, current sensors, etc., to obtain the current output current and output voltage of the inverter.

[0077] See Figure 2 , Figure 2 This is a structural block diagram of the current controller for an inverter provided in an embodiment of this application. Figure 2 As shown, the controller includes a voltage acquisition unit 201, a virtual impedance unit 202, and a drive unit 203. It is understood that, in order to better reflect the various data flows of the controller controlling the output current of the inverter, this application divides the controller into multiple units according to function. In actual product applications, the controller in this application is mainly manifested as at least one chip or multiple chips capable of establishing communication connections.

[0078] Controller (e.g.) Figure 2 The voltage acquisition unit 201 shown can acquire the first drive voltage of the inverter based on the inverter's reference voltage parameters. These reference voltage parameters include the reference voltage amplitude and the reference voltage frequency.

[0079] This reference voltage parameter is determined by the controller based on the inverter's reference power, the inverter's actual output power, and the mapping relationship between power and voltage parameters. For example, the inverter's reference power includes the reference active power P. ref and reference reactive power Q refThe actual output power of the inverter includes the actual active power P and the actual reactive power Q. The mapping relationship between power and voltage parameters can include the mapping relationship between active power and voltage frequency and the mapping relationship between reactive power and voltage amplitude.

[0080] The controller is based on the reference active power P ref The actual active power P and the mapping relationship between active power and voltage frequency are used to determine the reference voltage frequency W of the inverter. ref The controller can also adjust the reference reactive power Q. ref The actual reactive power Q and the mapping relationship between reactive power and voltage amplitude are used to determine the reference voltage amplitude V of the inverter. ref .

[0081] Optional, referencing active power P ref and reference reactive power Q ref It can be a pre-set fixed value.

[0082] The actual active power P and actual reactive power Q can be calculated by the controller. For example, the controller's input is coupled with voltage and current sensors. Taking this inverter as a three-phase inverter, including phases U, V, and W, the controller obtains the AC voltage v output by each phase of the inverter from the voltage sensors. u v v and v w The AC current i output of each phase is obtained from the current sensor. u i v and i w The phase difference θ between the voltage and current of each phase is obtained based on the AC voltage and AC current output by each phase of the inverter. u θ v and θ w The phase difference between each phase voltage and current can be obtained by referring to the zero-crossing detection method in existing technology, which will not be elaborated here. At this point, the actual active power P and the actual reactive power Q can be expressed as:

[0083]

[0084] In some feasible implementations, the mapping relationship between active power and voltage frequency can be found in [reference needed]. Figure 3A , Figure 3A The droop characteristic curve between active power and voltage frequency is provided for the embodiments of the application. Figure 3A As shown, the mapping relationship between active power and voltage frequency can be expressed as:

[0085] W ref =K P (PP ref )+WO Formula 2

[0086] Among them W O K represents the rated voltage frequency of the inverter. P It is the active power droop factor, which can be understood as... Figure 3A The slope of the curve is shown in the figure. W O With K P These are all device attributes of the inverter, and are related to the inverter model and / or manufacturer.

[0087] The mapping relationship between reactive power and voltage amplitude can be found in [reference needed]. Figure 3B , Figure 3B The droop control characteristic curve between reactive power and voltage amplitude is provided for embodiments of this application. Figure 3B As shown, the mapping relationship between reactive power and voltage amplitude can be expressed as:

[0088] V ref =K Q (QQ ref )+V O Formula 3

[0089] Where V O K represents the rated voltage amplitude of the inverter. Q It is the reactive power droop factor, which can be understood as... Figure 3B The slope of the curve shown in the figure. V O With K Q These are all device attributes of the inverter, and are related to the inverter model and / or manufacturer.

[0090] Optionally, in some feasible implementations, the controller may store a reference active power P. ref The actual active power P and the mapping relationship between active power and voltage frequency are obtained by looking up a table to get the inverter's reference voltage frequency W. ref Similarly, the controller can also store a reference reactive power Q. ref The actual reactive power Q and the mapping relationship between reactive power and voltage amplitude are obtained by looking up the table to get the inverter's reference voltage amplitude V. ref .

[0091] The controller uses the reference voltage frequency W ref Integrating the phases, we obtain the reference phase θ. Taking a three-phase inverter as an example, consisting of phases U, V, and W, where the phase voltages of phases U, V, and W have the same amplitude but a phase difference of 120°, the first drive voltage of this inverter can be expressed as:

[0092]

[0093] If the inverter is a single-phase inverter, then the first drive voltage of the single-phase inverter can be directly expressed as the U-phase voltage m. U .

[0094] The controller determines the second drive voltage of the inverter based on the first drive voltage and the damping voltage of the inverter.

[0095] The damping voltage of the inverter is controlled by the controller (e.g.) Figure 2 The virtual impedance unit 202 shown is determined based on the virtual impedance value of the inverter and the current output current of the inverter.

[0096] In some feasible implementations, the controller is equipped with a first preset current threshold I. TH The first preset current threshold can be understood as the safe current for the inverter to operate normally, and its specific value depends on the inverter model and / or manufacturer. The controller obtains the current output current I of the inverter, and when the current output current I of the inverter is not less than the first preset current threshold I... TH When the current output current of the inverter is less than the first preset current threshold, the controller sets the virtual impedance value to a constant non-zero value R, at which point the virtual impedance unit 202 is active. When the current output current of the inverter is less than the first preset current threshold, the controller sets the virtual impedance unit to zero, at which point the virtual impedance unit 202 is inactive. This can be expressed by the following formula:

[0097]

[0098] Where R a This is a virtual impedance.

[0099] Optionally, in some feasible implementations, the controller can determine a virtual impedance value based on the difference between the inverter's current output current and a first preset current threshold, as well as a first preset impedance value. In this case, the adjustment capability of the virtual impedance value can change according to the magnitude of the inverter's current output current; the magnitude of the inverter's current output current is directly proportional to the magnitude of the virtual impedance value. In other words, if the inverter's current output current I exceeds the first preset current threshold I... TH When there are many such instances, the controller sets a larger virtual impedance value; the current output current I of the inverter exceeds the first preset current threshold I. TH When the impedance is low, the controller sets a smaller virtual impedance value, which can be expressed by the following formula:

[0100]

[0101] R0 is a preset reference impedance value, which can be configured based on practical experience, for example, it can be 220Ω.

[0102] In implementing the embodiments of this application, the virtual impedance value changes with the magnitude of the inverter's output current, making the inverter's second drive voltage more accurate and adaptable.

[0103] The virtual impedance value R is determined by formula 5 or formula 6 above. a See Figure 4 , Figure 4 This is a schematic diagram illustrating the calculation of virtual impedance provided in an embodiment of this application. Figure 4 As shown, even if the inverter is a three-phase inverter, the virtual impedance value corresponding to the three-phase inverter is the same, which is simple, convenient and requires less calculation.

[0104] Optionally, in some feasible implementations, the inverter is a three-phase inverter, including phases U, V, and W. The controller is configured with respective second preset current thresholds I for phases U, V, and W. uTH I vTH and I wTH I uTH I vTH and I wTH The current can be the same or different. The controller compares the output current of each inverter phase with its corresponding second preset current threshold. When the output current of any inverter phase is not less than the corresponding second preset current threshold, the controller sets the corresponding virtual impedance value to a constant non-zero value, such as R1, R2, or R3. This can be expressed by the following formula:

[0105]

[0106] R ua R va and R wa These are the virtual impedance values ​​for phases U, V, and W of the inverter, respectively.

[0107] Optionally, in some feasible implementations, the controller can determine the virtual impedance value of each phase in the inverter based on the difference between the output current of each phase and the corresponding second preset current threshold of the inverter, as well as the second preset impedance values, such as R4, R5, or R6. This can be expressed by the following formula:

[0108]

[0109] See Figure 5 , Figure 5 This is another schematic diagram illustrating the calculation of virtual impedance provided in an embodiment of this application. For example... Figure 5As shown, the controller calculates the corresponding virtual impedance values ​​of each inverter. Compared with Formula 5 or Formula 6, where each inverter has a corresponding virtual impedance value, implementing the embodiment of this application can independently determine the output current of each phase of the inverter and calculate the virtual impedance value of each phase of the inverter separately. The results obtained are more accurate and applicable to scenarios where each phase of the inverter experiences a mismatch fault, making it more versatile.

[0110] The virtual impedance value of the inverter can be determined using formulas 5, 6, 7, or 8 above. Then, the controller, according to Ohm's law, multiplies the virtual impedance value by the current output current of the inverter to obtain the damping voltage of the inverter. It can be understood that if the inverter is a three-phase inverter, the damping voltage consists of three damping voltages. The controller determines the corresponding damping voltage based on the virtual impedance value of each phase and the current output current of each phase in the inverter.

[0111] Furthermore, the controller subtracts the inverter's damping voltage from the first drive voltage to obtain the inverter's second drive voltage. For example, taking a three-phase inverter as an example, including U, V, and W phases, the controller calculates the second drive voltage based on the first drive voltage of each phase in the inverter, for example, m... U m V and m W And the corresponding damping voltages, to determine the corresponding second drive voltages in the inverter, for example, V. u V v and V w .

[0112] Controller (e.g.) Figure 2 The drive unit 203 shown generates a drive signal based on the second drive voltage and sends the drive signal to the inverter. The drive signal is used to control the output current of the inverter. It can be understood that, taking a three-phase inverter as an example, the controller generates each drive signal based on the corresponding second drive voltage in the inverter and sends the corresponding drive signal to each phase of the inverter. Each drive signal corresponds to each phase of the inverter, and each drive signal controls the output current of each phase of the inverter.

[0113] The specific method by which the controller generates the drive signal based on the second drive voltage can refer to existing technologies. For example, the drive signal can be a pulse width modulation (PWM) wave. The controller compares the second drive voltage with a preset high-frequency carrier wave. If the second drive voltage is lower than the preset high-frequency carrier wave, a high level of the PWM wave is generated; if the second drive voltage is higher than the preset high-frequency carrier wave, a low level of the PWM wave is generated. The controller sends the generated PWM wave to the inverter. The inverter switches between on and off states based on the PWM wave. How the inverter switches states based on the PWM wave can refer to existing inverter control methods, such as PWM modulation, space vector pulse width modulation (SVPWM), discontinuous pulse width modulation (DPWM), etc., which will not be elaborated in the embodiments of this application.

[0114] It is understood that the driving unit 203 can be the same chip as the voltage acquisition unit 201 and the virtual impedance unit 202, or it can be an independent PWM generation chip.

[0115] The longer the inverter's on-time, the larger its output current. In other words, the inverter's output current is related to the drive signal, which is determined by the second drive voltage. In this embodiment, the controller determines the damping voltage by comparing the inverter's current output current with the virtual impedance value. This damping voltage is then subtracted from the first drive voltage to obtain the second drive voltage, which is used to generate the drive signal. By implementing this embodiment, the damping voltage can directly change the inverter's drive voltage, thereby generating a new drive signal and controlling the inverter's output current.

[0116] Furthermore, in this embodiment, the reference power can be determined by the controller based on the inverter's output voltage, the inverter's rated voltage, and the inverter's preset power, which includes preset reactive power and rated apparent power. For specific implementation details, see [link to implementation details]. Figure 6 , Figure 6 This is another structural block diagram of the current controller for the inverter provided in an embodiment of this application. (See diagram below.) Figure 6 As shown, the controller (e.g.) Figure 6The reference power determination unit 601 shown in the diagram determines the reference reactive power of the inverter based on the inverter's output voltage, the inverter's rated voltage, and a preset reactive power when the inverter's output voltage is lower than a preset voltage threshold. For example, the controller can reduce the preset reactive power according to the ratio between the inverter's output voltage and its rated voltage; or, for example, the controller can reduce the preset power according to the difference between the inverter's output voltage and its rated voltage. This embodiment does not limit how the reference reactive power is calculated. When the inverter's output voltage is not lower than the preset voltage threshold, the inverter's reference reactive power is the preset reactive power.

[0117] Taking the example of the controller reducing the preset reactive power according to the ratio between the inverter's output voltage and the inverter's rated voltage, the inverter's reference reactive power Q ref It can be represented as:

[0118]

[0119] Where Q0 is the preset reactive power, V g V is the output voltage of the inverter. O This refers to the rated voltage of the inverter. Q0 and V... O This refers to the device attributes of the inverter, which are related to the inverter model and / or manufacturer. g This voltage can be obtained by the controller from the sensor. V1 is a preset voltage threshold, which can be set according to different application conditions, for example, V1 = 0.9V. O .

[0120] When the inverter's output voltage is lower than a preset voltage threshold, the controller adjusts the inverter's reference reactive power Q. ref The output voltage V of the inverter g The rated voltage V of the inverter O And the rated apparent power S, determine the reference active power P of the inverter. ref The sum of the squares of active power and reactive power equals the square of apparent power. In some feasible implementations, the controller can subtract the square of the aforementioned reference reactive power from the square of the inverter's rated apparent power to obtain the square of the reference active power. Optionally, the controller can reduce the inverter's rated apparent power according to the ratio between the inverter's output voltage and its rated voltage before calculating the inverter's reference active power, as expressed by the formula:

[0121]

[0122] P0 is the preset reactive power, which is a device attribute of the inverter and is related to the inverter model and / or manufacturer.

[0123] Controller (e.g.) Figure 4 The actual power calculation unit 602 shown in the figure obtains the current output current and output voltage of the inverter and calculates the actual output power of the inverter. For specific calculations, please refer to the previous text. Figure 2 Formula 1, as described, will not be elaborated upon here.

[0124] Controller (e.g.) Figure 4 The reference voltage parameter determination unit 603 shown in the diagram determines the inverter's reference voltage parameters based on the reference power determined by the reference power determination unit 601 and the actual output power calculated by the actual power calculation unit 602. The inverter's reference voltage parameters can be found in the preceding text. Figures 3A to 3B The described embodiments are intended to illustrate that, after determining the voltage reference parameters, the controller can refer to the foregoing text in conjunction with... Figure 2 The described embodiment directly changes the inverter's drive voltage to generate a new drive signal and controls the inverter's output current; this will not be elaborated upon here.

[0125] The embodiments of this application, in conjunction with the foregoing description, Figures 2 to 5 Based on the described embodiment, the determination of the reference power is added, so that when the output voltage of the inverter is lower than the preset voltage threshold, the controller can not only increase the damping voltage to change the drive voltage of the inverter, but also further control the reference power of the inverter, thereby controlling the output current of the inverter.

[0126] In some feasible implementations, embodiments of this application can also be implemented via a controller (e.g., Figure 4 The voltage / current loop unit 604 shown in the diagram determines the first drive voltage. At this time, the voltage / current loop unit 604 acquires the inverter's output voltage and the reference voltage parameter determined by the reference voltage parameter determination unit 603, and determines the inverter's reference current based on the inverter's output voltage and reference voltage parameter. The voltage / current loop unit 604 also acquires the inverter's current output current and determines the inverter's first drive voltage based on the inverter's current output current and the inverter's reference current. The first drive voltage is subtracted from the inverter's damping voltage to obtain the second drive voltage. In this embodiment, the damping voltage is directly calculated with the first drive voltage output by the voltage / current loop unit, without being limited by the bandwidth of the voltage / current loop unit, and is not affected by the delay of the voltage / current loop unit. Implementing this embodiment, the inverter's current control system responds effectively and quickly.

[0127] To illustrate that the current control system of the inverter provided in this application can control the inverter's output current, especially when the inverter's output voltage is lower than a preset voltage threshold, the inventors of this application conducted comparative experiments on not implementing the embodiments of this application, using the constant non-zero virtual impedance value of the embodiments of this application, and using the variable virtual impedance value of the embodiments of this application. See [link to relevant documentation] Figure 7 , Figure 7 This is a schematic diagram illustrating the effect of implementing an embodiment of this application. For example... Figure 7 As shown, curve 1 corresponds to the inverter's output current without implementing the embodiments of this application; curve 2 corresponds to the inverter's output current when using a constant non-zero virtual impedance value (i.e., the virtual impedance corresponding to formula 5 above) in the embodiments of this application; and curve 3 corresponds to the inverter's output current when using a variable virtual impedance (i.e., the virtual impedance corresponding to formula 6 above) in the embodiments of this application. Time t1 is the moment when the inverter's output voltage drops below a preset voltage threshold, and time t2 is the moment when the inverter's output current drops below a first preset current threshold. From Figure 7 As can be seen, when the inverter's output voltage drops below the preset voltage threshold, the current in curve 1 increases sharply. This can be interpreted as the current in the inverter's current control system increasing rapidly, potentially damaging the semiconductor devices within the inverter. In contrast, the current changes in curves 2 and 3 are gradual, effectively protecting the inverter's equipment. When the inverter's output current drops below the first preset current threshold (i.e., at time t2), the virtual impedance value can be zero. Since curve 2 represents a constant, non-zero virtual impedance value, it needs to be reset to zero at time t2. This causes a significant increase in the inverter's output current, posing a risk of inverter damage. Curve 3, however, maintains a gradual current change, effectively protecting the inverter and demonstrating strong adaptability.

[0128] This application also provides a current controller for an inverter, which includes a transceiver, a processor, and a memory.

[0129] The transceiver includes, but is not limited to, receiving the inverter's current output current and output voltage, and sending drive signals to the inverter. The memory stores instructions and can be double-datarate synchronous dynamic random access memory (DDR SDRAM) or other types of cache. The processor can be, but is not limited to, an application processor, one or more microprocessors, a digital signal processor (DSP), a microcontroller unit (MCU), or an artificial intelligence processor. The processor executes the aforementioned commands by calling the instructions stored in memory. Figures 2 to 6 Any of the embodiments described.

[0130] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0131] The division of units in this application is merely a logical functional division. In actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed.

[0132] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs.

[0133] In addition, in the various embodiments of the present invention, each functional unit can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0134] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A current control system for an inverter, characterized in that, The current control system includes a DC power supply, an inverter, an AC load, and a controller, wherein the input terminal of the inverter is coupled to the DC power supply, the output terminal of the inverter is coupled to the AC load, and the control terminal of the inverter is coupled to the controller. The controller is configured to determine the reference voltage frequency of the inverter based on the inverter's reference active power, actual active power, and the mapping relationship between active power and voltage frequency; and to determine the reference voltage amplitude of the inverter based on the inverter's reference reactive power, actual reactive power, and the mapping relationship between reactive power and voltage amplitude. The controller is further configured to obtain a first drive voltage of the inverter based on a reference voltage parameter of the inverter; the reference voltage parameter includes the reference voltage amplitude and the reference voltage frequency; The controller is further configured to subtract the first driving voltage from the damping voltage of the inverter to obtain the second driving voltage of the inverter; the damping voltage of the inverter is determined based on the virtual impedance value of the inverter and the current output current of the inverter, wherein the virtual impedance value is a constant non-zero value or zero set based on the comparison result of the current output current of the inverter and a first preset current threshold, or is determined based on the difference between the current output current of the inverter and the first preset current threshold and the first preset impedance value; The controller is further configured to generate a drive signal based on the second drive voltage and send the drive signal to the inverter, the drive signal being used to control the output current of the inverter.

2. The current control system according to claim 1, characterized in that, The controller is also configured to determine the reference power of the inverter based on the output voltage of the inverter, the rated voltage of the inverter, and the preset power of the inverter.

3. The current control system according to claim 2, characterized in that, The preset power includes preset reactive power and rated apparent power; The controller is further configured to determine the reference reactive power of the inverter based on the output voltage of the inverter, the rated voltage of the inverter, and the preset reactive power. The controller is further configured to determine the reference active power of the inverter based on the inverter's reference reactive power, the inverter's output voltage, the inverter's rated voltage, and the rated apparent power.

4. The current control system according to claim 1, characterized in that, The controller is further configured to perform an integral operation based on the reference voltage frequency of the inverter to obtain a reference phase, and determine the first drive voltage of the inverter based on the reference phase and the reference voltage amplitude.

5. The current control system according to any one of claims 1-4, characterized in that, The inverter includes a three-phase inverter; The controller is configured to determine the corresponding second drive voltage of each phase in the three-phase inverter based on the first drive voltage of each phase and the corresponding damping voltage of each phase; wherein the corresponding damping voltage of each phase in the three-phase inverter is determined based on the virtual impedance value of each phase in the three-phase inverter and the corresponding output current of each phase in the three-phase inverter. The controller is further configured to generate each drive signal according to the corresponding second drive voltage in the three-phase inverter, and send the corresponding drive signal to each phase in the three-phase inverter respectively, wherein each drive signal is used to control the output current of each phase in the three-phase inverter.

6. The current control system according to claim 5, characterized in that, The controller is further configured to determine the virtual impedance value of each phase in the three-phase inverter based on the difference between the output current of each phase in the three-phase inverter and the corresponding second preset current threshold of each phase in the three-phase inverter, as well as the second preset impedance value.

7. The current control system according to claim 2, characterized in that, The inverter's output voltage is lower than a preset voltage threshold.

8. A current control method for an inverter, characterized in that, The inverter's input terminal is coupled to a DC power supply, the inverter's output terminal is coupled to an AC load, and the inverter's control terminal is coupled to a current controller. The current control method is applicable to the current controller and includes: The reference voltage frequency of the inverter is determined based on the reference active power, the actual active power, and the mapping relationship between active power and voltage frequency; the reference voltage amplitude of the inverter is determined based on the reference reactive power, the actual reactive power, and the mapping relationship between reactive power and voltage amplitude. The first drive voltage of the inverter is obtained based on the reference voltage parameters of the inverter; the reference voltage parameters include the reference voltage amplitude and the reference voltage frequency; The first driving voltage is subtracted from the damping voltage of the inverter to obtain the second driving voltage of the inverter; the damping voltage of the inverter is determined based on the virtual impedance value of the inverter and the current output current of the inverter. The virtual impedance value is a constant non-zero value or zero set based on the comparison result between the current output current of the inverter and the first preset current threshold, or it is determined based on the difference between the current output current of the inverter and the first preset current threshold and the first preset impedance value. A drive signal is generated based on the second drive voltage and sent to the inverter. The drive signal is used to control the output current of the inverter.

9. The current control method according to claim 8, characterized in that, The reference power of the inverter is determined based on the inverter's output voltage, the inverter's rated voltage, and the inverter's preset power.

10. The current control method according to claim 9, characterized in that, The preset power of the inverter includes the preset reactive power of the inverter and the rated apparent power of the inverter; The reference reactive power of the inverter is determined based on the output voltage of the inverter, the rated voltage of the inverter, and the preset reactive power. The reference active power of the inverter is determined based on the reference reactive power of the inverter, the output voltage of the inverter, the rated voltage of the inverter, and the rated apparent power of the inverter.

11. The current control method according to claim 8, characterized in that, The step of obtaining the first drive voltage of the inverter based on the reference voltage parameters of the inverter includes: The reference phase is obtained by integrating the reference voltage frequency of the inverter, and the first drive voltage of the inverter is determined based on the reference phase and the reference voltage amplitude.

12. The current control method according to any one of claims 8-11, characterized in that, The inverter includes a three-phase inverter; Determining the second drive voltage of the inverter based on the first drive voltage and the damping voltage of the inverter includes: Based on the first driving voltage of each phase in the three-phase inverter and the corresponding damping voltage, the corresponding second driving voltage in the three-phase inverter is determined; wherein the corresponding damping voltage in the three-phase inverter is determined based on the virtual impedance value of each phase in the three-phase inverter and the corresponding output current in the three-phase inverter. The step of generating a drive signal based on the second drive voltage and sending the drive signal to the inverter includes: Each drive signal is generated according to the corresponding second drive voltage in the three-phase inverter, and the corresponding drive signal is sent to each phase of the three-phase inverter. Each drive signal is used to control the output current of each phase in the three-phase inverter.

13. The current control method according to claim 12, characterized in that, The virtual impedance value of each phase in the inverter is determined based on the difference between the output current of each phase in the three-phase inverter and the corresponding second preset current threshold of the three-phase inverter, as well as the respective second preset impedance value.

14. The current control method according to claim 9, characterized in that, The inverter's output voltage is lower than a preset voltage threshold.

15. A current controller for an inverter, characterized in that, The current controller includes a transceiver, a processor, and a memory, wherein the transceiver, the processor, and the memory are coupled via a bus system. The transceiver is used to receive the current output current and output voltage of the inverter, and to send drive signals to the inverter. The memory is used to store instructions; The processor is used to invoke instructions stored in the memory to execute the method of any one of claims 8-14.

Images