Three-level energy storage converter and control method and control device thereof

Abstract

The invention discloses a control method of a three-level energy storage converter. The method comprises the following steps: acquiring a positive half bus voltage, a negative half bus voltage and a power parameter of the three-level energy storage converter; obtaining a voltage feedback quantity at least according to the positive half bus voltage and the negative half bus voltage, wherein the voltage feedback quantity can represent the difference between the negative half bus voltage and the positive half bus voltage; in response to the condition that the power parameter is in a preset power interval and the voltage feedback quantity is outside a preset voltage interval, providing a common-mode signal and superposing the common-mode signal to a three-phase voltage modulation wave of the three-level energy storage converter so as to suppress midpoint potential deviation of the three-level energy storage converter; and in response to the condition that the power parameter is in the preset power interval and the voltage feedback quantity is in the preset voltage interval, performing zero clearing treatment on the common-mode signal superposed on the three-phase voltage modulation wave. The neutral point of the bus potential of the three-level energy storage converter can be kept balanced, and equipment damage is avoided.

Description

Technical Field

[0001] The present application relates to the field of electric power supply regulation, and in particular to a three-level energy storage converter and a control method and a control device thereof. Background Art

[0002] In the prior art, in order to maintain the bus midpoint potential balance, there is a method of maintaining the bus midpoint potential balance by adding a balancing bridge circuit, but this method increases the cost, and the addition of a balancing bridge circuit will cause the energy storage inverter to heat up severely, thereby increasing the heat dissipation cost; in addition, there is also a method of injecting a common-mode voltage according to a given direction of the active current to achieve bus midpoint balance, but in the case of low power, due to the sampling deviation, the active current direction cannot be accurately judged, which may cause the bus midpoint potential balance control to fail, and then cause the energy storage inverter to fail. Summary of the invention

[0003] In order to solve the deficiencies of the prior art, this application adopts the following technical solutions: In a first aspect, the present application provides a control method for a three-level energy storage converter, the control method comprising the following steps: Collecting the positive half bus voltage, negative half bus voltage and power parameters of the three-level energy storage converter, where the power parameters represent the active power of the three-level energy storage converter; At least obtaining a voltage feedback amount according to the positive half bus voltage and the negative half bus voltage, wherein the voltage feedback amount can represent a difference between the negative half bus voltage and the positive half bus voltage; In response to the power parameter being within a preset power range and the voltage feedback amount being outside a preset voltage range, providing a common mode signal to be superimposed on a three-phase voltage modulation wave of a three-level energy storage converter to suppress a midpoint potential deviation of the three-level energy storage converter; In response to the power parameter being within a preset power range and the voltage feedback amount being within a preset voltage range, the common mode signal superimposed on the three-phase voltage modulation wave is cleared.

[0004] The control method of the three-level energy storage converter provided in the present application determines whether the current state of the three-level energy storage converter belongs to the working condition of small active power according to whether the power parameter is in a preset power interval; and under the working condition of small active power, determines the bus midpoint potential offset according to the voltage feedback amount. If the voltage feedback amount is within the preset voltage interval, it indicates that the bus midpoint potential offset is small in the current state of the three-level energy storage converter. At this time, no intervention measures are taken for the energy storage converter, thereby avoiding erroneous intervention on the energy storage converter when the direction of the midpoint potential offset of the energy storage converter is difficult to accurately judge, and avoiding further deviation of the bus midpoint potential causing energy storage converter failure; if the voltage feedback amount is outside the preset voltage interval, it indicates that the bus midpoint potential offset of the three-level energy storage converter in the current state is large. At this time, a common-mode signal is provided to be superimposed on the three-phase voltage modulation wave of the inverter, thereby maintaining the bus midpoint voltage balance, thereby improving the stability of the equipment.

[0005] Furthermore, in response to the power parameter being within a preset power range and the voltage feedback amount being outside a preset voltage range, a positive common mode signal is provided.

[0006] Furthermore, it is defined that when the system in which the three-level energy storage converter is located is in a discharging condition, the power parameter is positive; In response to the power parameter being outside the preset power range and the voltage feedback amount being outside the preset voltage range, If the power parameter is positive and the negative half bus voltage is greater than the positive half bus voltage, a negative common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is positive and the negative half bus voltage is less than the positive half bus voltage, a positive common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; Furthermore, it is defined that when the system in which the three-level energy storage converter is located is in a charging condition, the power parameter is negative; In response to the power parameter being outside the preset power range and the voltage feedback amount being outside the preset voltage range, If the power parameter is negative and the negative half bus voltage is greater than the positive half bus voltage, a positive common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is negative and the negative half bus voltage is less than the positive half bus voltage, a negative common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter.

[0007] Furthermore, the voltage feedback amount is obtained by calculating the difference between the negative half bus voltage and the positive half bus voltage; The control method also includes: Provide a benchmark; The reference quantity and the voltage feedback quantity are processed to obtain the error quantity; Perform control operation based on the error amount to obtain a midpoint compensation signal; The midpoint compensation signal is inverted or not inverted to obtain a common mode signal; The control operation is any one of the following types of control operations: P control operation, PI control operation, PIR control operation; and the reference value is 0.

[0008] Furthermore, the method also includes: In response to the power parameter being outside the preset power range, if the power parameter is positive, the midpoint compensation signal is not inverted and the midpoint compensation signal is a common mode signal; if the power parameter is negative, the midpoint compensation signal is inverted to obtain a common mode signal.

[0009] Furthermore, the method also includes: In response to the power parameter being within a preset power range, if the error amount is positive, the midpoint compensation signal is not inverted and the midpoint compensation signal is a common mode signal; if the error amount is negative, the midpoint compensation signal is inverted to obtain a common mode signal.

[0010] In a second aspect, the present application further provides a control device for a three-level energy storage converter, the control device comprising: A collection unit, used to collect the positive half bus voltage, negative half bus voltage and power parameters of the three-level energy storage converter; A calculation unit, used for obtaining a voltage feedback amount according to at least a negative half bus voltage and a positive half bus voltage; A compensation unit, used for providing a common-mode signal, in response to the power parameter being within a preset power interval and the voltage feedback amount being outside a preset voltage interval, the compensation unit provides a common-mode signal to be superimposed on the three-phase voltage modulation wave of the three-level energy storage converter to suppress the midpoint potential deviation of the three-level energy storage converter; in response to the power parameter being within a preset power interval and the voltage feedback amount being within a preset voltage interval, the compensation unit clears the common-mode signal superimposed on the three-phase voltage modulation wave; The control unit receives the three-phase voltage modulation wave corrected by the compensation unit, and controls the three-level energy storage converter based on the corrected three-phase voltage modulation wave.

[0011] The control device of the three-level energy storage converter provided in the present application determines whether the current state of the three-level energy storage converter belongs to the working condition of small active power according to whether the power parameter is in a preset power interval; and under the working condition of small active power, determines the bus midpoint potential deviation according to the voltage feedback amount. If the voltage feedback amount is within the preset voltage interval, it indicates that the bus midpoint potential deviation is small in the current state of the three-level energy storage converter. At this time, no intervention measures are taken for the energy storage converter, thereby avoiding erroneous intervention on the energy storage converter when the direction of the midpoint potential deviation of the energy storage converter is difficult to accurately judge, and avoiding further deviation of the bus midpoint potential causing energy storage converter failure; if the voltage feedback amount is outside the preset voltage interval, it indicates that the bus midpoint potential deviation of the three-level energy storage converter in the current state is large. At this time, a common-mode signal is provided to be superimposed on the three-phase voltage modulation wave of the inverter, thereby maintaining the bus midpoint voltage balance, thereby improving the stability of the equipment.

[0012] Further, in response to the power parameter being within a preset power range and the voltage feedback amount being outside a preset voltage range, the compensation unit provides a positive common mode signal.

[0013] Further, it is defined that when the system where the three-level energy storage converter is located is in a discharging condition, the power parameter is positive; it is defined that when the system where the three-level energy storage converter is located is in a charging condition, the power parameter is negative; The compensation unit is also used to In response to the power parameter being outside the preset power range and the voltage feedback amount being outside the preset voltage range, If the power parameter is positive and the negative half bus voltage is greater than the positive half bus voltage, a negative common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is positive and the negative half bus voltage is less than the positive half bus voltage, a positive common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is negative and the negative half bus voltage is greater than the positive half bus voltage, a positive common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is negative and the negative half bus voltage is less than the positive half bus voltage, a negative common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter.

[0014] Furthermore, the compensation unit includes an error module, a calculation module and a processing module; the error module is used to perform a difference process between the reference amount and the voltage feedback amount to obtain an error amount; The operation module is used to perform control operation on the error amount to obtain a midpoint compensation signal; The processing module is used to perform inversion processing on the midpoint compensation signal or not perform inversion processing to obtain a common mode signal; Among them, the operation module is any one of the following types of control operations: P control operation module, PI control operation module, PIR control operation module; the reference amount is 0.

[0015] In a third aspect, the present application further provides a three-level energy storage converter, the three-level energy storage converter comprising a three-level inverter circuit and positive and negative bus capacitors, and the control device as described above. The three-level energy storage converter also has the advantage that the control device can maintain the midpoint potential balance, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic flow chart of a control method for a three-level energy storage converter provided in one embodiment of the present application; Figure 2 A signal processing block diagram provided for an embodiment of the present application; Figure 3 A flowchart of a three-level energy storage converter provided in an embodiment of the present application in actual use; Figure 4 A circuit diagram of a three-level energy storage converter provided in one embodiment of the present application. DETAILED DESCRIPTION

[0017] The present application will be described in detail below in conjunction with the specific implementation modes shown in the accompanying drawings, but these implementation modes do not limit the present application. Structural, methodological, or functional changes made by ordinary technicians in the field based on these implementation modes are included in the protection scope of the present application.

[0018] In order to solve the deficiencies of the prior art, in a first aspect, the present application provides a control method for a three-level energy storage converter, such as Figure 1 As shown, the method comprises the following steps: Step S11, collecting the positive half bus voltage, negative half bus voltage and power parameters of the three-level energy storage converter. The power parameter represents the active power, and the power parameter can be the active power itself, or the output current d-axis component, etc. For ease of explanation, the power parameter is described as the active power itself in the embodiment of the present application.

[0019] Step S12, obtaining a voltage feedback amount based on at least the positive half bus voltage and the negative half bus voltage, wherein the voltage feedback amount can characterize the difference between the negative half bus voltage and the positive half bus voltage. For ease of explanation, in the embodiment of the present application, the voltage feedback amount is obtained by calculating the difference between the negative half bus voltage and the positive half bus voltage. It is easy to understand that in some embodiments, the difference between the positive half bus voltage and the negative half bus voltage can also be used as the voltage feedback amount.

[0020] Step S13, in response to the power parameter being within the preset power range and the voltage feedback amount being outside the preset voltage range, providing a common mode signal to be superimposed on the three-phase voltage modulation wave of the three-level energy storage converter to suppress the midpoint potential deviation of the three-level energy storage converter; In response to the power parameter being within a preset power range and the voltage feedback amount being within a preset voltage range, the common mode signal superimposed on the three-phase voltage modulation wave is cleared.

[0021] In step S13, a preset power interval can be set based on the maximum sampling error. When the AC active power is within the preset power interval, the control method provided in the present application can avoid erroneous intervention in the energy storage inverter and avoid further deviation of the bus midpoint potential causing energy storage inverter failure.

[0022] Specifically, the control method of the three-level energy storage converter provided in the present application is based on the AC active power in the current state of the three-level energy storage converter. When it is determined that the current state of the three-level energy storage converter belongs to a working condition with relatively small active power (that is, the AC active power is within a preset power range), the difference between the negative half-bus voltage and the positive half-bus voltage is calculated to obtain a voltage feedback amount. If the voltage feedback amount is within the preset voltage range, the common-mode signal superimposed on the three-phase voltage modulation wave is cleared to zero, thereby avoiding erroneous intervention on the energy storage converter when the potential offset direction of the energy storage converter is difficult to accurately judge, and avoiding further deviation of the bus midpoint potential to cause a failure of the energy storage converter.

[0023] Furthermore, if the AC active power is within the preset power range and the voltage feedback is outside the preset voltage range, a common mode signal is provided and superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter to avoid equipment damage. The three-level energy storage converter provided by the present application does not require additional circuits, thereby avoiding increasing the cost of the three-level energy storage converter.

[0024] As an optional implementation, Figure 2 As shown, the present application provides a common mode signal including the following steps: Provide a benchmark; The reference quantity and the voltage feedback quantity are processed to obtain the error quantity; Perform control operation based on the error amount to obtain a midpoint compensation signal; The midpoint compensation signal is inverted or not inverted to obtain a common mode signal.

[0025] Specifically, for ease of explanation, in the embodiment of the present application, the collected positive half bus voltage is recorded as Vbus_p, the collected negative half bus voltage is recorded as Vbus_n, and the voltage feedback amount is recorded as (Vbus_n-Vbus_p). A reference amount is provided, and in the embodiment of the present application, the reference amount is set to 0, and the error amount is the result of subtracting the voltage feedback amount (Vbus_n-Vbus_p) from the reference amount, and the error amount is recorded as err.

[0026] A control operation is performed on the error err, and the control operation can be any of the following types of control operations: P control operation, PI control operation, and PIR control operation. Figure 2 As shown, in the embodiment of the present application, PI operation is used to process the error amount err to obtain a midpoint compensation signal, and the midpoint compensation signal is recorded as Δu. In one embodiment, Figure 2 The transfer function of the PI control operation is set as follows: G PI (s) = k p + k i / s; Among them, k p represents the proportionality coefficient, k i Represents the integral coefficient.

[0027] By inverting or not inverting the midpoint compensation signal Δu, a common-mode signal can be obtained, and the common-mode signal is recorded as Δuf. It is easy to understand that superimposing the common-mode signal on the three-phase voltage modulation wave of the three-level energy storage converter can affect the switching state of the three-level energy storage converter, thereby affecting the midpoint potential of the three-level energy storage converter, and suppressing the midpoint potential offset of the three-level energy storage converter.

[0028] When providing a common-mode signal, whether to invert the midpoint compensation signal needs to refer to the current charging and discharging state of the converter and the offset direction of the midpoint potential. The control strategy provided by this application will be described in detail below: For ease of explanation, the collected power parameter (AC active power in this application) is recorded as Pac.

[0029] In step S13, in response to the power parameter being within the preset power range and the voltage feedback amount being outside the preset voltage range, a positive common mode signal is provided.

[0030] Exemplarily, in an embodiment of the present application, the preset power interval is set to: greater than or equal to -2KW, and less than or equal to 2KW. The power interval in the present application includes endpoint values, and may not include endpoint values ​​in actual settings; the preset voltage interval is set to: greater than or equal to -10V, and less than or equal to 10V. The voltage interval in the present application includes endpoint values, and may not include endpoint values ​​in actual settings.

[0031] It should be noted that the preset power interval and voltage interval can be set according to actual needs. For example, the preset power interval can be configured to meet the following requirements: the preset power interval includes the maximum sampling error of the power. By setting it in this way, if the collected AC active power is within the preset power interval, no processing will be done until the voltage feedback amount is outside the preset voltage interval and then the common mode signal is superimposed on the three-phase voltage modulation wave. This can avoid erroneous intervention on the energy storage converter when the potential offset direction of the energy storage converter is difficult to accurately judge, and avoid further deviation of the bus midpoint potential causing energy storage converter failure.

[0032] Based on the above preset power range and voltage range, the following situations may exist in step 13: 1) The AC active power Pac is greater than or equal to -2KW and less than or equal to 2KW (that is, the power parameter is within the preset power range), and the voltage feedback amount (Vbus_n-Vbus_p) is greater than or equal to -10V and less than or equal to 10V (that is, the voltage feedback amount is within the preset power range). At this time, the common-mode signal superimposed on the three-phase voltage modulation wave is cleared to avoid erroneous intervention on the energy storage converter when the direction of the potential deviation of the energy storage converter is difficult to accurately determine, thereby avoiding further deviation of the bus midpoint potential and causing energy storage converter failure.

[0033] 2) The AC active power Pac is greater than or equal to -2KW and less than or equal to 2KW (that is, the power parameter is within the preset power range), and the voltage feedback amount (Vbus_n-Vbus_p) is less than -10V or greater than 10V (that is, the voltage feedback amount is outside the preset power range). At this time, a positive common-mode signal is provided and superimposed on the three-phase voltage modulation wave.

[0034] Specifically, Figure 2 For example, when the AC active power Pac is greater than or equal to -2KW and less than or equal to 2KW, if the voltage feedback amount (Vbus_n-Vbus_p) is less than -10V, the error amount err is greater than 0. A positive midpoint compensation signal can be obtained by performing PI control operation on the error amount err. If the midpoint compensation signal is not negated, a positive common-mode signal can be obtained.

[0035] When the AC active power Pac is greater than or equal to -2KW and less than or equal to 2KW, if the voltage feedback amount (Vbus_n-Vbus_p) is greater than 10V, the error amount err is less than 0. A negative midpoint compensation signal can be obtained by performing PI control operation on the error amount err. A positive common-mode signal can be obtained by inverting the midpoint compensation signal.

[0036] According to the above description, when -2KW≤Pac≤2KW and |Vbus_n-Vbus_p|>10V, a positive common-mode signal is provided to be superimposed on the three-phase voltage modulation wave of the three-level energy storage converter, so that the three-level energy storage converter can return to the state of |Vbus_n - Vbus_p| ≤ 10V, and maintain the dynamic balance under low power or reactive power operation.

[0037] Further, it is defined that when the system in which the three-level energy storage converter is located is in a discharging condition, the power parameter is positive; and when the system in which the three-level energy storage converter is located is in a charging condition, the power parameter is negative. The method provided by the present application also includes: Step S14: in response to the power parameter being outside the preset power range and the voltage feedback amount being outside the preset voltage range, If the power parameter is positive and the negative half bus voltage is greater than the positive half bus voltage (the voltage feedback is positive), a negative common mode signal is provided to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is positive and the negative half bus voltage is less than the positive half bus voltage (the voltage feedback amount is negative), a positive common mode signal is provided to suppress the midpoint potential deviation of the three-level energy storage converter.

[0038] Step S15: In response to the power parameter being outside the preset power range and the voltage feedback amount being outside the preset voltage range, If the power parameter is negative and the negative half bus voltage is greater than the positive half bus voltage (the voltage feedback is positive), a positive common mode signal is provided to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is negative and the negative half bus voltage is less than the positive half bus voltage (the voltage feedback amount is negative), a negative common mode signal is provided to suppress the midpoint potential deviation of the three-level energy storage converter.

[0039] In step S14 and step S15, in response to the power parameter being outside the preset power range, if the power parameter is positive, the midpoint compensation signal is not inverted and the midpoint compensation signal is used as the common-mode signal; if the power parameter is negative, the midpoint compensation signal is inverted to obtain the common-mode signal.

[0040] Specifically, in step S14, the power parameter is outside the preset power range and is positive, which means that the AC active power Pac is greater than the preset power 2KW. It is determined that the three-level energy storage converter is in a discharge condition at this time, the inverter is in a step-down mode, and the electric energy is transferred from the energy storage battery to the grid or load. Further, the following situations exist: 1) When the negative half-bus voltage Vbus_n is greater than the positive half-bus voltage Vbus_p, the voltage feedback is positive, the error err is less than 0, and the midpoint compensation Δu obtained after the control operation is less than 0. The midpoint compensation Δu is not inverted to obtain a negative common-mode signal, which is superimposed on the inverter three-phase voltage modulation wave. The control signal controls the inverter switch tube, thereby increasing the positive half-bus voltage Vbus_p and reducing the negative half-bus voltage Vbus_n, so as to achieve a balanced bus midpoint potential of the three-level energy storage converter and avoid equipment damage.

[0041] 2) When the negative half-bus voltage Vbus_n is less than the positive half-bus voltage Vbus_p, the voltage feedback is negative, the error err is greater than 0, and the midpoint compensation Δu obtained after the control operation is greater than 0. The midpoint compensation Δu is not inverted to obtain a positive common-mode signal, which is superimposed on the inverter three-phase voltage modulation wave. The control signal controls the inverter switch tube, thereby reducing the positive half-bus voltage Vbus_p and increasing the negative half-bus voltage Vbus_n, so as to achieve a balanced bus midpoint potential of the three-level energy storage converter and avoid equipment damage.

[0042] Specifically, in step S15, the power parameter is outside the preset power range and is negative, which means that the AC active power Pac is less than the preset power -2KW, and it is determined that the three-level energy storage converter is in the charging state at this time, and the energy storage battery is charged. Further, there are the following situations: 1) When the negative half-bus voltage Vbus_n is greater than the positive half-bus voltage Vbus_p, the voltage feedback is positive and the error err is less than 0. The midpoint compensation Δu obtained after the control operation is less than 0. The midpoint compensation Δu is inverted to obtain a positive common-mode signal, which is superimposed on the inverter three-phase voltage modulation wave. The control signal controls the inverter switch tube, thereby increasing the positive half-bus voltage Vbus_p and reducing the negative half-bus voltage Vbus_n, so as to achieve a balanced bus midpoint potential of the three-level energy storage converter and avoid equipment damage.

[0043] 2) When the negative half-bus voltage Vbus_n is less than the positive half-bus voltage Vbus_p, the voltage feedback is negative, the error err is greater than 0, and the midpoint compensation Δu obtained after the control operation is greater than 0. The midpoint compensation Δu is inverted to obtain a negative common-mode signal, which is superimposed on the inverter three-phase voltage modulation wave. The control signal controls the inverter switch tube, thereby reducing the positive half-bus voltage Vbus_p and increasing the negative half-bus voltage Vbus_n, so as to achieve a balanced bus midpoint potential of the three-level energy storage converter and avoid equipment damage.

[0044] To further illustrate the control method provided by this application, Figure 3 As shown, a control logic block diagram of a control method for a three-level energy storage converter of the present application is provided. It includes: Collect the positive half bus voltage, negative half bus voltage and AC active power of the three-level energy storage converter; Calculate the difference between the negative half bus voltage and the positive half bus voltage to obtain a voltage feedback amount, and compare a reference amount (set to 0 in this application) with the voltage feedback amount to calculate an error amount; When the AC active power is greater than 2kw and the midpoint potential of the converter is offset, the output of the PI controller (i.e. the midpoint compensation amount) is not inverted; When the AC active power is less than -2kw and the midpoint potential of the converter is offset, the output of the PI controller is inverted; When the AC active power is greater than or equal to -2kw and less than or equal to 2kw, if Vbus_p-Vbus_n≥10V, the output of the PI controller is not inverted; if Vbus_p-Vbus_n≤-10V, the output of the PI controller is inverted. If | Vbus_p-Vbus_n |≤10V, the output of the PI controller is cleared.

[0045] The above Figure 3 Processing and Figure 2 The corresponding common-mode signal can be obtained by combining the signal processing shown in the figure, and the common-mode signal is superimposed on the inverter three-phase voltage modulation wave to maintain the balance of the bus midpoint voltage and avoid equipment damage.

[0046] like Figure 2 As shown, in order to achieve control of power transmission, the SWPWM control module will generate corresponding PWM signals according to UA / UB / UC / Ubus_p / Vbus_n and output them to the control end of the three-level NPC circuit switch tube to achieve charge and discharge control. According to the above description, by superimposing the above control method for midpoint voltage balance control, it is beneficial to maintain midpoint voltage balance. A / U B / U Cis the three-phase modulation voltage output by the current loop, V bus_p / V bus_n The positive and negative half-bus voltages are obtained by sampling. The control method of the three-level energy storage converter of the present application is based on the AC active power of the three-level energy storage converter in the current state. When it is determined that the current state of the three-level energy storage converter belongs to the working condition with small active power, the difference between the negative half-bus voltage and the positive half-bus voltage is calculated to obtain the voltage feedback amount. If the voltage feedback amount is within the preset voltage range, it is determined that the bus midpoint potential offset is small in the current state of the energy storage converter, and no intervention measures are taken on the energy storage converter, thereby avoiding the energy storage converter from being subjected to erroneous intervention when the direction of the midpoint potential offset of the energy storage converter is difficult to accurately judge, and avoiding the energy storage converter from being further deviated from by the bus midpoint potential and causing the energy storage converter to fail. If the voltage feedback amount is outside the preset voltage range, a positive common-mode signal is provided to be superimposed on the inverter three-phase voltage modulation wave, thereby maintaining the bus midpoint voltage balance and avoiding equipment damage.

[0047] In a second aspect, the present application further provides a control device for a three-level energy storage converter, the control device comprising: A collection unit, used to collect the positive half bus voltage, negative half bus voltage and power parameters of the three-level energy storage converter; A calculation unit, used for obtaining a voltage feedback amount according to at least a negative half bus voltage and a positive half bus voltage; A compensation unit, used for providing a common-mode signal, in response to the power parameter being within a preset power interval and the voltage feedback amount being outside a preset voltage interval, the compensation unit provides a common-mode signal to be superimposed on the three-phase voltage modulation wave of the three-level energy storage converter to suppress the midpoint potential deviation of the three-level energy storage converter; in response to the power parameter being within a preset power interval and the voltage feedback amount being within a preset voltage interval, the compensation unit clears the common-mode signal superimposed on the three-phase voltage modulation wave; The control unit receives the three-phase voltage modulation wave corrected by the compensation unit, and controls the three-level energy storage converter based on the corrected three-phase voltage modulation wave.

[0048] The above-mentioned control device applies the control method provided in the present application to the three-level energy storage converter, and its effect is the same as the effect of the control method provided in the present application, which will not be described in detail here.

[0049] As an optional implementation, in the control device provided in the embodiment of the present application, in response to a power parameter being within a preset power range and a voltage feedback amount being outside a preset voltage range, the compensation unit provides a positive common-mode signal.

[0050] It is defined that when the system in which the three-level energy storage converter is located is in a discharging condition, the power parameter is positive; it is defined that when the system in which the three-level energy storage converter is located is in a charging condition, the power parameter is negative. As an optional implementation, in the control device provided in the embodiment of the present application, the compensation unit is also used for: In response to the power parameter being outside the preset power range and the voltage feedback amount being outside the preset voltage range, If the power parameter is positive and the negative half bus voltage is greater than the positive half bus voltage, a negative common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is positive and the negative half bus voltage is less than the positive half bus voltage, a positive common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is negative and the negative half bus voltage is greater than the positive half bus voltage, a positive common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is negative and the negative half bus voltage is less than the positive half bus voltage, a negative common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter.

[0051] As an optional implementation, in the control device provided in the embodiment of the present application, the compensation unit includes an error module, a calculation module and a processing module; the error module is used to perform a difference process between the reference amount and the voltage feedback amount to obtain an error amount; The operation module is used to perform control operation on the error amount to obtain a midpoint compensation signal; The processing module is used to perform inversion processing on the midpoint compensation signal or not perform inversion processing to obtain a common mode signal; Among them, the operation module is any one of the following types of control operations: P control operation module, PI control operation module, PIR control operation module; the reference amount is 0.

[0052] In a third aspect, the present application further provides a three-level energy storage converter, the three-level energy storage converter comprising a three-level inverter circuit and positive and negative bus capacitors, and a control device provided by the present application. Exemplarily, the three-level inverter circuit and the positive and negative bus capacitors are as follows: Figure 4 As shown, the positive bus capacitor is C1 and the negative bus capacitor is C2.

[0053] It will be appreciated that the word "exemplary" as used herein means "serving as an example, instance, or illustration". Any embodiment described as "exemplary" is not necessarily preferred or superior to other embodiments and / or does not exclude the combination of features of other embodiments. It will be appreciated that certain features of the present application described in the context of separate embodiments for the sake of clarity may also be provided in a single embodiment by combination. Conversely, various features of the present application described in the context of a single embodiment for the sake of clarity may also be provided individually or in any suitable combination or as any other described embodiment of the present application.

[0054] The above disclosure is only the preferred embodiment of the present application, but it is not intended to limit the scope of rights of the present application. A person of ordinary skill in the art can understand that without departing from the spirit and scope of the present application and the appended claims, changes, modifications, substitutions, combinations, and simplifications should all be equivalent replacement methods and still fall within the scope of the invention.

Claims

1. A control method for a three-level energy storage converter, characterized in that: The control method comprises the following steps: Collecting a positive half bus voltage, a negative half bus voltage and a power parameter of the three-level energy storage converter, wherein the power parameter represents the active power of the three-level energy storage converter; Obtaining a voltage feedback amount at least according to the positive half-bus voltage and the negative half-bus voltage, wherein the voltage feedback amount can represent a difference between the negative half-bus voltage and the positive half-bus voltage; In response to the power parameter being within a preset power range and the voltage feedback amount being outside a preset voltage range, providing a common mode signal to be superimposed on a three-phase voltage modulation wave of the three-level energy storage converter to suppress a midpoint potential deviation of the three-level energy storage converter; In response to the power parameter being within a preset power range and the voltage feedback amount being within a preset voltage range, the common mode signal superimposed on the three-phase voltage modulation wave is cleared.

2. The control method according to claim 1, characterized in that: In response to the power parameter being within a preset power range and the voltage feedback amount being outside a preset voltage range, a positive common mode signal is provided.

3. The control method according to claim 1, characterized in that: It is defined that when the system in which the three-level energy storage converter is located is in a discharging condition, the power parameter is positive; In response to the power parameter being outside a preset power range and the voltage feedback amount being outside a preset voltage range, If the power parameter is positive and the negative half-bus voltage is greater than the positive half-bus voltage, a negative common-mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is positive and the negative half bus voltage is less than the positive half bus voltage, a positive common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter.

4. The control method according to claim 1, characterized in that: It is defined that when the system in which the three-level energy storage converter is located is in a charging condition, the power parameter is negative; In response to the power parameter being outside a preset power range and the voltage feedback amount being outside a preset voltage range, If the power parameter is negative and the negative half-bus voltage is greater than the positive half-bus voltage, a positive common-mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is negative and the negative half bus voltage is less than the positive half bus voltage, a negative common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter.

5. The control method according to any one of claims 1 to 4, characterized in that: The voltage feedback amount is obtained by calculating the difference between the negative half bus voltage and the positive half bus voltage; The control method further comprises: Provide a benchmark; Performing a difference process between the reference amount and the voltage feedback amount to obtain an error amount; Performing a control operation based on the error amount to obtain a midpoint compensation signal; Performing an inversion process on the midpoint compensation signal or not performing an inversion process to obtain the common mode signal; Wherein, the control operation is any one of the following types of control operations: P control operation, PI control operation, PIR control operation; and the reference value is 0.

6. The control method according to claim 5, characterized in that: The method further comprises: In response to the power parameter being outside a preset power range, if the power parameter is positive, the midpoint compensation signal is not inverted and the midpoint compensation signal is the common-mode signal; if the power parameter is negative, the midpoint compensation signal is inverted to obtain the common-mode signal.

7. The control method according to claim 5, characterized in that: The method further comprises: In response to the power parameter being within a preset power range, if the error amount is positive, the midpoint compensation signal is not inverted and the midpoint compensation signal is the common-mode signal; if the error amount is negative, the midpoint compensation signal is inverted to obtain the common-mode signal.

8. A control device for a three-level energy storage converter, characterized in that: The control device comprises: A collection unit, used for collecting the positive half bus voltage, negative half bus voltage and power parameters of the three-level energy storage converter; a calculation unit, configured to obtain a voltage feedback amount at least according to the negative half-bus voltage and the positive half-bus voltage; A compensation unit, configured to provide a common-mode signal, in response to the power parameter being within a preset power interval and the voltage feedback amount being outside a preset voltage interval, the compensation unit provides a common-mode signal to be superimposed on the three-phase voltage modulation wave of the three-level energy storage converter to suppress the midpoint potential deviation of the three-level energy storage converter; in response to the power parameter being within a preset power interval and the voltage feedback amount being within a preset voltage interval, the compensation unit clears and disposes of the common-mode signal superimposed on the three-phase voltage modulation wave; A control unit receives the three-phase voltage modulation wave corrected by the compensation unit, and controls the three-level energy storage converter based on the corrected three-phase voltage modulation wave.

9. The control device according to claim 8, characterized in that: In response to the power parameter being within a preset power range and the voltage feedback amount being outside a preset voltage range, the compensation unit provides a positive common mode signal.

10. The control device according to claim 8 or 9, characterized in that: It is defined that when the system in which the three-level energy storage converter is located is in a discharging condition, the power parameter is positive; it is defined that when the system in which the three-level energy storage converter is located is in a charging condition, the power parameter is negative; The compensation unit is also used for: In response to the power parameter being outside a preset power range and the voltage feedback amount being outside a preset voltage range, If the power parameter is positive and the negative half-bus voltage is greater than the positive half-bus voltage, a negative common-mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is positive and the negative half-bus voltage is less than the positive half-bus voltage, a positive common-mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is negative and the negative half-bus voltage is greater than the positive half-bus voltage, a positive common-mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter; If the power parameter is negative and the negative half bus voltage is less than the positive half bus voltage, a negative common mode signal is provided to be superimposed on the three-phase voltage modulation wave to suppress the midpoint potential deviation of the three-level energy storage converter.

11. The control device according to claim 8 or 9, characterized in that: The compensation unit includes an error module, a calculation module and a processing module; the error module is used to perform a difference process between the reference amount and the voltage feedback amount to obtain an error amount; The operation module is used to perform control operation on the error amount to obtain a midpoint compensation signal; The processing module is used to perform an inversion process on the midpoint compensation signal or not perform an inversion process to obtain the common mode signal; Wherein, the operation module is any one of the following types of control operations: P control operation module, PI control operation module, PIR control operation module; and the reference amount is 0.

12. A three-level energy storage converter, characterized in that: The three-level energy storage converter comprises a three-level inverter circuit and positive and negative bus capacitors, and a control device as described in any one of claims 8 to 11.

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