Hierarchical system communication-free distributed control method and device

Abstract

The application provides a kind of cascade system communication-free distributed control method and device, the method comprises: the output of the AC current of the power module is adjusted as bridge arm voltage reference value after closed loop control;Observe the bridge arm voltage reference value and obtain the bridge arm voltage, and the bridge arm voltage is used as feedback signal, and the bridge arm voltage reference value is controlled after the AC current of the power module is adjusted together after closed loop control, and the bridge arm voltage is controlled according to the bridge arm voltage reference value;Wherein, in at least one working mode of the cascade system, the change of the parameter reflecting the active current is monotonous with the change of the bridge arm voltage.According to the embodiment of the application, the bridge arm voltage of each power module is consistent in the method by closed loop control, and communication coordination is not needed between each power module, and the system can also be stable under communication failure.

Description

Technical Field

[0001] This application relates to the field of distributed control technology for cascaded systems, and in particular to a non-communication distributed control method and apparatus for cascaded systems. Background Technology

[0002] In existing cascaded systems, the controller is typically mounted locally on the power modules to form a distributed control system, which gives the modular cascaded system excellent flexibility, scalability, and reliability. However, a significant challenge in the distributed control of cascaded systems is the DC-link voltage consistency control of the modules, i.e., voltage equalization control. Conventional voltage equalization control methods adjust the voltage of their own bridge arms based on the relative magnitude of the voltage of the power module and the average voltage of the modules. The drawback of this method is that it requires communication lines to obtain the voltages of other modules, placing high demands on the reliability of communication. In practical communication, it is even more necessary for the system to continue operating stably without relying on communication after a communication failure, or to eliminate the need for communication altogether, reducing the complexity of system communication connections. This poses an even greater challenge to control technology. Summary of the Invention

[0003] In this context, one aspect of this disclosure is to provide a non-communication distributed control method for cascaded systems, in which closed-loop control ensures that the arm voltages of each power module are consistent, no communication coordination is required between the power modules, and the system can operate stably even in the event of a communication failure.

[0004] According to one aspect of this disclosure, a non-communication distributed control method for a cascaded system is provided, wherein at least two power modules are cascaded to form a cascaded system, and each power module includes a control module; the method includes:

[0005] The output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value.

[0006] The bridge arm voltage is obtained by observing the bridge arm voltage reference value, and the bridge arm voltage is used as a feedback signal. After being jointly adjusted by the AC current of the power module through closed-loop control, the bridge arm voltage reference value is controlled.

[0007] Control the bridge arm voltage according to the bridge arm voltage reference value;

[0008] In at least one operating mode of the cascaded system, the change in the parameter reflecting the active current is monotonic with the change in the arm voltage.

[0009] Optionally, the arm voltage is obtained by observing the arm voltage reference value, and the arm voltage is used as a feedback signal. After passing through closed-loop control together with the AC current of the power module, the arm voltage reference value is controlled, including:

[0010] The arm voltage is compared with the arm voltage setpoint and superimposed on the active current setpoint in a reverse droop manner, i.e.:

[0011] I drefi =I dset -K VbI (V bset -V bi )

[0012] Among them, I drefi I is the active current reference value for the i-th power module. dset The active current setpoint, V bset V is the bridge arm voltage setting value. bi K is the bridge arm voltage. VbI The active current-bridge arm voltage anti-droop coefficient is the active current reference value, which is a parameter reflecting the active current.

[0013] Optionally, the set value V of the bridge arm voltage bset Take the rated voltage of the power grid.

[0014] Optionally, the value obtained by multiplying the d-axis component of the bridge arm voltage by the active current reference value, and then comparing it with the value obtained by multiplying the q-axis component of the bridge arm voltage by the reactive current reference value, is used as the AC current reference value.

[0015]

[0016] Among them, i gref I is the reference value for alternating current. dref I is the active current reference value. qref The reactive current reference value is; the bridge arm voltage is v bx For a sinusoidal fundamental signal in phase with the bridge arm voltage, v by For lag v bx A 90-degree sine wave signal.

[0017] Optionally, the output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value, including:

[0018] Sample alternating current;

[0019] The AC current reference value is compared with the AC current to generate a current error. After the current error is adjusted by the current regulator, the sinusoidal fundamental signal of the bridge arm voltage in phase is added as feedforward to obtain the bridge arm voltage reference value.

[0020] Optionally, the method of obtaining the bridge arm voltage by observing the bridge arm voltage reference value, and using the bridge arm voltage as a feedback signal, which, together with the AC current of the power module, undergoes closed-loop control to control the bridge arm voltage reference value, further includes:

[0021] The bridge arm voltage was observed after the reference value of the bridge arm voltage was obtained by performing a second-order generalized integral.

[0022] Optionally, the method further includes:

[0023] The arm voltage is compared with the arm voltage setpoint and superimposed on the DC link voltage setpoint in a reverse drooping manner, i.e.:

[0024] v dcrefi =v dcset -K vb (V bset -V bi );

[0025] Among them, v dcrefi This is the reference value for the DC link voltage, v dcset V is the DC link voltage setpoint. bset V is the bridge arm voltage setting value. bi K is the bridge arm voltage. vb This is the anti-droop control coefficient.

[0026] Optionally, the method further includes:

[0027] When there is communication and coordination between the control modules of each power module, the DC link voltage setting value is compared with the DC link voltage to generate a DC link voltage error. The initial DC link voltage error of the other power module is used as a feedforward, coordinated and integrated, and then superimposed on the bridge arm voltage setting value.

[0028] Optionally, the bridge arm voltages of the at least two power modules are the same.

[0029] Optionally, the power module includes an AC-DC converter and a DC-DC converter, wherein the AC-DC converter is controlled by the cascaded system's non-communication distributed control method.

[0030] Optionally, the DC-DC converter employs DC link voltage droop control or output current droop control.

[0031] Optionally, the control in the DC-DC converter may also include a secondary regulation loop.

[0032] According to one aspect of this disclosure, a non-communication distributed control method for a three-phase system is provided, wherein each single phase includes at least one power module, and each power module includes a control module; the method includes:

[0033] At least two power modules are cascaded to form a cascaded system, and each power module includes a control module; the method includes:

[0034] The output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value.

[0035] The bridge arm voltage is obtained by observing the bridge arm voltage reference value, and the bridge arm voltage is used as a feedback signal. After being jointly adjusted by the AC current of the power module through closed-loop control, the bridge arm voltage reference value is controlled.

[0036] Control the bridge arm voltage according to the bridge arm voltage reference value;

[0037] In at least one operating mode of the cascaded system, the change in the parameter reflecting the active current is monotonic with the change in the arm voltage.

[0038] Optionally, the arm voltage is obtained by observing the arm voltage reference value, and the arm voltage is used as a feedback signal. After passing through closed-loop control together with the AC current of the power module, the arm voltage reference value is controlled, including:

[0039] The arm voltage is compared with the arm voltage setpoint and superimposed on the active current setpoint in a reverse droop manner, i.e.:

[0040] I drefi =I dset -K VbI (V bset -V bi )

[0041] Among them, I drefi I is the active current reference value for the i-th power module. dset The active current setpoint, V bset V is the bridge arm voltage setting value. bi K is the bridge arm voltage. VbI The active current-bridge arm voltage anti-droop coefficient is the active current reference value, which is a parameter reflecting the active current.

[0042] Optionally, the set value V of the bridge arm voltage bset Take the rated voltage of the power grid.

[0043] Optionally, the value obtained by multiplying the d-axis component of the bridge arm voltage by the active current reference value, and then comparing it with the value obtained by multiplying the q-axis component of the bridge arm voltage by the reactive current reference value, is used as the AC current reference value, i.e.:

[0044]

[0045] Among them, i gref I is the reference value for alternating current. dref I is the active current reference value. qref The reactive current reference value is; the bridge arm voltage is v bx For a sinusoidal fundamental signal in phase with the bridge arm voltage, v by For lag v bx A 90-degree sine wave signal.

[0046] Optionally, the output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value, including:

[0047] Sample alternating current;

[0048] The AC current reference value is compared with the AC current to generate a current error. After the current error is adjusted by the current regulator, the sinusoidal fundamental signal of the bridge arm voltage in phase is added as feedforward to obtain the bridge arm voltage reference value.

[0049] Optionally, the method of observing the bridge arm voltage reference value to obtain the bridge arm voltage, and using the bridge arm voltage as a feedback signal, together with the AC current of the power module, undergoes closed-loop control to control the bridge arm voltage reference value, including:

[0050] The bridge arm voltage was observed after the reference value of the bridge arm voltage was obtained by performing a second-order generalized integral.

[0051] Optionally, the method further includes:

[0052] The arm voltage is compared with the arm voltage setpoint and superimposed on the DC link voltage setpoint in a reverse drooping manner, i.e.:

[0053] v dcrefi =v dcset -K vb (V bset -V bi );

[0054] Among them, v dcrefi This is the reference value for the DC link voltage, v dcset V is the DC link voltage setpoint. bset V is the bridge arm voltage setting value. bi K is the bridge arm voltage. vb This is the anti-droop control coefficient.

[0055] Optionally, the method further includes:

[0056] When there is communication and coordination between the control modules of each power module, the DC link voltage setting value is compared with the DC link voltage to generate a DC link voltage error. The initial DC link voltage error of the other power module is used as a feedforward, coordinated and integrated, and then superimposed on the bridge arm voltage setting value.

[0057] Optionally, the bridge arm voltages of the at least two power modules are the same.

[0058] Optionally, the power module includes an AC-DC converter and a DC-DC converter, wherein the AC-DC converter is controlled by the cascaded system's non-communication distributed control method.

[0059] Optionally, the DC-DC converter employs DC link voltage droop control or output current droop control.

[0060] Optionally, the control in the DC-DC converter may also include a secondary regulation loop.

[0061] According to one aspect of this disclosure, a non-communication distributed control device for a cascaded system is provided, wherein at least two power modules are cascaded to form a cascaded system, and each power module includes a control module, the control module being used for:

[0062] The output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value.

[0063] The bridge arm voltage is obtained by observing the bridge arm voltage reference value, and the bridge arm voltage is used as a feedback signal. After being jointly adjusted by the AC current of the power module through closed-loop control, the bridge arm voltage reference value is controlled.

[0064] Control the bridge arm voltage according to the bridge arm voltage reference value;

[0065] In at least one operating mode of the cascaded system, the change in the parameter reflecting the active current is monotonic with the change in the arm voltage.

[0066] Optionally, the arm voltage is obtained by observing the arm voltage reference value, and the arm voltage is used as a feedback signal. After passing through closed-loop control together with the AC current of the power module, the arm voltage reference value is controlled, including:

[0067] The arm voltage is compared with the arm voltage setpoint and superimposed on the active current setpoint in a reverse droop manner, i.e.:

[0068] I drefi =I dset -K VbI (V bset -V bi )

[0069] Among them, I drefi I is the active current reference value for the i-th power module. dset The active current setpoint, V bset V is the bridge arm voltage setting value. bi K is the bridge arm voltage. VbI The active current-bridge arm voltage anti-droop coefficient is the active current reference value, which is a parameter reflecting the active current.

[0070] Optionally, the value obtained by multiplying the d-axis component of the bridge arm voltage by the active current reference value, and then comparing it with the value obtained by multiplying the q-axis component of the bridge arm voltage by the reactive current reference value, is used as the AC current reference value.

[0071]

[0072] Among them, i gref I is the reference value for alternating current. dref I is the active current reference value. qref The reactive current reference value is; the bridge arm voltage is v bx For a sinusoidal fundamental signal in phase with the bridge arm voltage, v by For lag v bx A 90-degree sine wave signal.

[0073] Optionally, the output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value, including:

[0074] Sample alternating current;

[0075] The AC current reference value is compared with the AC current to generate a current error. After the current error is adjusted by the current regulator, the sinusoidal fundamental signal of the bridge arm voltage in phase is added as feedforward to obtain the bridge arm voltage reference value.

[0076] Optionally, the method of observing the bridge arm voltage reference value to obtain the bridge arm voltage, and using the bridge arm voltage as a feedback signal, together with the AC current of the power module, undergoes closed-loop control to control the bridge arm voltage reference value, including:

[0077] The bridge arm voltage was observed after the reference value of the bridge arm voltage was obtained by performing a second-order generalized integral.

[0078] Optionally, the control module is further configured to:

[0079] The arm voltage is compared with the arm voltage setpoint and superimposed on the DC link voltage setpoint in a reverse drooping manner, i.e.:

[0080] vdcrefi =v dcset -K vb (V bset -V bi );

[0081] Among them, v dcrefi This is the reference value for the DC link voltage, v dcset V is the DC link voltage setpoint. bset V is the bridge arm voltage setting value. bi K is the bridge arm voltage. vb This is the anti-droop control coefficient.

[0082] Optionally, the control module is further configured to:

[0083] When there is communication and coordination between the control modules of each power module, the DC link voltage setting value is compared with the DC link voltage to generate a DC link voltage error. The initial DC link voltage error of the other power module is used as a feedforward, coordinated and integrated, and then superimposed on the bridge arm voltage setting value.

[0084] The above embodiments provide a communication-free distributed control method for cascaded systems. By sampling and feedback control of the AC current, the output of the control loop is the bridge arm voltage. Then, by observing the bridge arm voltage and using closed-loop control, the bridge arm voltages of each power module are made consistent. This method enables the active current parameter to change monotonically with the bridge arm voltage in at least one operating mode of the system. No communication coordination is required between the power modules, and the system can operate stably even in the event of a communication failure. Attached Figure Description

[0085] The above and other objects, features and advantages of this disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0086] Figure 1 This is the circuit schematic of a cascaded system;

[0087] Figure 2 A flowchart illustrating a non-communication distributed control method for a cascaded system according to an embodiment of this disclosure;

[0088] Figure 3 The overall logic block diagram of the non-communication distributed control method for cascaded systems;

[0089] Figure 4 Detailed logic block diagram of a non-communication distributed control method for a cascaded system;

[0090] Figure 5 This is a block diagram of the DC link voltage-bridge arm voltage anti-droop control logic.

[0091] Figure 6 The control effect diagram shows the control effect under different anti-droop control coefficients;

[0092] Figure 7 Control effect under different loads

[0093] Figure 8 Diagrams showing the control effect under different reactive power conditions;

[0094] Figure 9 This is a diagram illustrating the control effect under varying grid voltage.

[0095] Figure 10 This is a logic block diagram of a distributed control method under the communication mode of a cascaded system.

[0096] Figure 11 The diagram illustrates the implementation effect of an example with coordinated integrals;

[0097] Figure 12 This is a control block diagram of the DC-DC converter in an SST cascade system.

[0098] Figure 13 An implementation diagram illustrating the effect of an example of SST A2D level non-communication distributed control;

[0099] Figure 14 This is a block diagram of a three-phase cascaded system. Detailed Implementation

[0100] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0101] It should be noted that when assigning reference numerals to components in the figures in this specification, although the same reference numerals are shown in different figures, the same reference numerals shall, as far as possible, represent the same components. Furthermore, in the description below of this disclosure, detailed descriptions of known functions and constructions incorporated herein will be omitted where such detailed descriptions would make the subject matter of this disclosure considerably unclear.

[0102] Furthermore, when describing elements of this disclosure, terms such as “first,” “second,” “A,” “B,” “(a),” and “(b)” may be used herein. These terms are used only to distinguish one element from other elements, and the nature, order, sequence, or number of the corresponding elements are not limited by these terms. When an element is described as being “connected to,” “coupled to,” or “linked to” another element, it will be understood that an element may not only be directly connected to or coupled to another element, but may also be “connected to,” “coupled to,” or “linked to” another element via a third element, or the third element may be inserted between one element and another element.

[0103] Furthermore, references to "an embodiment," "an embodiment," "an example embodiment," etc., indicate that the described embodiment may include specific features, structures, or characteristics, but not every embodiment must include these specific features, structures, or characteristics. Moreover, such statements do not refer to the same embodiment. Furthermore, when describing specific features, structures, or characteristics in connection with embodiments, whether or not explicitly described, it is indicated that incorporating such features, structures, or characteristics into other embodiments is within the knowledge of those skilled in the art.

[0104] Furthermore, certain terms are used in the specification and subsequent claims to refer to specific components or parts. Those skilled in the art will understand that manufacturers may use different names or terms to refer to the same component or part. This specification and subsequent claims do not distinguish components or parts by differences in name, but rather by differences in function. The terms "comprising" and "including" used throughout the specification and subsequent claims are open-ended and should be interpreted as "including but not limited to." Additionally, the term "connection" here includes any direct and indirect electrical connection means, including connections via other means.

[0105] As an example, such as Figure 1 , Figure 2 , Figure 3 As shown, Figure 1 This is the circuit schematic of a cascaded system. Figure 2 This is a flowchart illustrating a non-communication distributed control method for a cascaded system according to an embodiment of the present disclosure. Figure 3 The overall logic block diagram of the non-communication distributed control method for cascaded systems;

[0106] like Figure 1 The cascaded system shown consists of at least two cascaded power modules with a voltage v b1 v b2 ...v bNThis represents the bridge arm voltage of each power module.

[0107] The control method in this embodiment is designed for distributed control without communication in the cascaded system. Each power module includes a control module, and the control methods of each power module are set in the same way, such as 2. Figure 3 As shown, the method includes:

[0108] S1. The output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value v. biref ;

[0109] The output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value v. biref ,include:

[0110] Sample alternating current;

[0111] A current error is generated by comparing the AC current reference value with the AC current. After the current error is adjusted by the current regulator, the sinusoidal fundamental signal of the bridge arm voltage in phase is added as a feedforward to obtain the bridge arm voltage reference value v. biref .

[0112] S2. Observe the bridge arm voltage reference value v. biref The bridge arm voltage v is obtained bi and the bridge arm voltage v bi As a feedback signal, it, together with the AC current of the power module, undergoes closed-loop control regulation to control the bridge arm voltage reference value v. biref ;

[0113] In at least one operating mode of the cascaded system, the change in the parameter reflecting the active current is monotonic with the change in the arm voltage.

[0114] Since the current in a cascaded system is consistent, the magnitude of the bridge arm voltage reflects the amount of power absorbed by each power module. By using closed-loop control to make the bridge arm voltage consistent, the power absorbed by the power modules becomes consistent, and the bridge arm voltages of at least two power modules are the same.

[0115] like Figure 4 As shown, Figure 4 The diagram shows a specific logic block diagram of a non-communication distributed control method for a cascaded system. In the specific implementation, the reference value v of the bridge arm voltage is observed. biref The bridge arm voltage v is obtained bi The bridge arm voltage is used as the feedback signal v. bi After passing through closed-loop control together with the AC current of the power module, the reference value v of the bridge arm voltage is controlled. biref Specifically, it includes:

[0116] The bridge arm voltage reference value v biref After second-order generalized integration, the bridge arm voltage V was observed. bi ;

[0117] The arm voltage is compared with the arm voltage setpoint and superimposed on the active current setpoint in a reverse droop manner to obtain the active current reference value. The arm voltage and the active current setpoint form a reverse droop relationship, that is:

[0118] I drefi =I dset -K VbI (V bset -V bi )

[0119] Among them, I drefi I is the reference value for the active current of the i-th power module; dset The active current setting is set to the same value for all modules or to zero; V bset The bridge arm voltage setting value is taken as the grid rated voltage. V bi K is the bridge arm voltage. VbI The active current-bridge arm voltage anti-droop coefficient is the active current reference value, which is a parameter reflecting the active current.

[0120] Then, the d-axis component of the bridge arm voltage is... With the active current reference value I dref The value after multiplication is the same as the q-axis component of the bridge arm voltage. With reactive current reference value I qref The multiplied values ​​are compared and used as the reference value i for the alternating current. gref To achieve closed-loop control, that is

[0121]

[0122] Among them, i gref I is the reference value for alternating current. dref I is the active current reference value. qref The reactive current reference value is; the bridge arm voltage is v bx For a sinusoidal fundamental signal in phase with the bridge arm voltage, v by For lag v bx A 90-degree sine wave signal.

[0123] The smaller the bridge arm voltage, the smaller the DC-Link voltage setpoint, i.e., the DC-Link voltage reference value. For scenarios where the DC-Link voltage is fixed, such as a battery voltage, sampling the aforementioned current loop control is sufficient, with the active current setpoint I... dsetThe active current setting can be set according to the system's required active current. For scenarios where the DC-link voltage is a capacitor and the DC load varies, the active current setting value I... dset It can be generated by the DC-link voltage outer loop.

[0124] like Figure 5 As shown, for scenarios requiring control of the DC-link voltage, this embodiment further proposes that the DC-link-bridge arm voltage adopt anti-droop control, superimposed on the reference value of the DC-link voltage, that is:

[0125] The bridge arm voltage V bi With bridge arm voltage setting value V bset In comparison, the voltage v is superimposed on the DC link voltage setpoint in the form of a reverse droop. dcset Control the DC link voltage reference value v dcrefi ,Right now:

[0126] v dcrefi =v dcset -K vb (V bset -V bi );

[0127] Among them, v dcrefi This is the reference value for the DC link voltage, v dcset This is the DC link voltage setting value. (V) bset This is the bridge arm voltage setting value, which can be taken as the grid rated voltage. V bi K is the bridge arm voltage. vb The anti-droop control factor is the bridge arm voltage V. bi The smaller the value, the lower the DC link voltage reference value v. dcrefi The smaller it is.

[0128] The design of an anti-droop control system must consider both system stability and the steady-state error of the DC-link voltage. For the anti-droop control coefficient K... vb The design methodology is as follows:

[0129] The mathematical model of the system in the dq coordinate system is as follows:

[0130]

[0131] The governing equation model is as follows:

[0132] v bd1 =-K pI (K pVdc (v dcset -K Vb (V bset -V b1 )-vdc1 )-i gd )+V b1

[0133] The bridge arm voltage observer model is

[0134]

[0135] Based on the above equations, the differential model can be obtained as follows:

[0136]

[0137] Where, a0 = K pI K pVdc K Vb γ,

[0138] The stability condition is b0 < 0, 1 + b1T d >0, a0-b1+b0T d >0.

[0139] Since b0 < 0, it can be seen that in i dc When the value is greater than 0, i.e. during rectification operation, it must meet the following requirements.

[0140] In addition, an excessively large anti-droop factor will result in a large steady-state error in the DC-Link voltage. Therefore, a compromise needs to be made in designing the anti-droop factor, with the preferred range being [2,5].

[0141] Taking the rectification of a cascaded system consisting of two power modules as an example, Figure 6 To illustrate the control effect under different anti-droop coefficients, when K Vb When = 1, as shown in Figure (a), the system is unstable, and the DC-link voltage of the two power modules is V. dc1 v dc2 The error grows larger and larger, thus diverging. When K Vb When K = 2, as shown in Figure (b), the system is stable, but the convergence speed is slow; when K = 2, the system is stable, but the convergence speed is slow. Vb =5 converges faster, as shown in Figure (c). Figure 7 The control effects under different loads are shown in Figure (a), where the heavy load state is displayed. dc =10A, the heavier the load, the faster the convergence; where (b) shows the light load state, i dc =1A, it is stable even under light load. Figure 8 To illustrate the control effect under reactive power conditions, Figure (a) shows the reactive power absorption state, and Figure (b) shows the reactive power generation state. The system is stable under both reactive power absorption and reactive power generation conditions. Figure 9To illustrate the control effect under changes in grid voltage, Figure (a) shows the state where the grid voltage drops by 5%, and Figure (b) shows the state where the grid voltage rises by 5%. The figures show that when the grid voltage changes, the DC-link voltage will have a steady-state error. This is because this control method usually cannot obtain the grid voltage when there is no communication, and the bridge arm voltage setpoint does not change in time with the change in the grid voltage amplitude.

[0142] The control method provided in the above embodiments is for control of a cascaded system in a distributed mode without communication. However, it is applicable when there is communication and coordination between the control modules of each power module. Figure 10 As shown, Figure 10 This is a control logic block diagram for the coordinated communication of control modules of each power module in a cascaded system according to the embodiments of this disclosure. Based on the non-communication distributed control method of the above embodiments, the DC link voltage setpoint v is... dcset With DC link voltage v dci The DC link voltage integral state quantity Intj of the other power module is compared with the DC link voltage integral state quantity Int of this module. i In comparison, the above two, after coordinated integration, produce the DC chain voltage integral state quantity Int. i This is superimposed on the bridge arm voltage setting value v. dcset superior. Figure 11 The implementation effect of the embodiment with coordination integral is shown. When there is communication coordination between the control modules of each power module, the control method with coordination integral can be adopted, that is, there is no steady-state error in steady state. Under communication failure, integration is no longer performed, and it degenerates into the distributed control method in the non-communication mode of the above embodiment, which can enable the system to continue to operate stably, thereby greatly improving the reliability of the system.

[0143] The control method provided by this invention can be applied to an SST cascade system, comprising an AC-DC converter and a DC-DC converter, wherein the AC-DC converter adopts... Figure 4 The cascaded system shown lacks a communication-based distributed control method. The DC-DC converter can employ DC link voltage droop control or output current droop control combined with a secondary regulation loop. Figure 12 The diagram shows the control block diagram of the DC-DC converter in the SST cascade system. (a) shows the DC link voltage droop control, and (b) shows the droop control combined with the secondary regulation loop. The specific methods will not be described in detail in this application. Figure 13The implementation effect of AC-DC level non-communication distributed control in SST is shown in Figure (a), where the grid voltage drops by 10% and Figure (b) shows the grid voltage rises by 10%. When the grid voltage changes, the DC link voltage will have a certain steady-state error. Since the grid voltage is not sampled in the control, the bridge arm voltage setpoint does not change in time with the change of the grid voltage amplitude. This steady-state error is the characteristic of anti-droop. SST can operate stably.

[0144] This application also provides a non-communication distributed control method for a three-phase system, the schematic diagram of which is shown below. Figure 14 As shown, each single phase includes at least one power module, and each power module includes a control module. The control module samples and provides feedback control of the AC current of the power module. The output of the control module is the arm voltage. The control module observes the amplitude of the arm voltage and performs closed-loop control. In at least one operating mode of the system, the parameter reflecting the active current changes monotonically with the change of the arm voltage.

[0145] like Figure 2 , Figure 3 As shown, the method includes:

[0146] S1. The output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value v. biref ;

[0147] The output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value v. biref ,include:

[0148] Sample alternating current;

[0149] A current error is generated by comparing the AC current reference value with the AC current. After the current error is adjusted by the current regulator, the sinusoidal fundamental signal with the same phase as the bridge arm voltage is added as a feedforward to obtain the bridge arm voltage reference value v. biref .

[0150] S2. Observe the bridge arm voltage reference value v. biref The bridge arm voltage v is obtained bi and the bridge arm voltage v bi As a feedback signal, it, together with the AC current of the power module, undergoes closed-loop control regulation to control the bridge arm voltage reference value v. biref ;

[0151] In at least one operating mode of the cascaded system, the change in the parameter reflecting the active current is monotonic with the change in the arm voltage.

[0152] Since the current in a cascaded system is consistent, the magnitude of the bridge arm voltage reflects the amount of power absorbed by each power module. By using closed-loop control to make the bridge arm voltage consistent, the power absorbed by the power modules becomes consistent, and the bridge arm voltages of at least two power modules are the same.

[0153] like Figure 4 As shown, Figure 4 The diagram shows a specific logic block diagram of a non-communication distributed control method for a cascaded system. In the specific implementation, the reference value v of the bridge arm voltage is observed. biref The bridge arm voltage v is obtained bi The bridge arm voltage is used as the feedback signal v. bi After passing through closed-loop control together with the AC current of the power module, the reference value v of the bridge arm voltage is controlled. biref Specifically, it includes:

[0154] The bridge arm voltage reference value v biref After second-order generalized integration, the bridge arm voltage V was observed. bi ;

[0155] The arm voltage is compared with the arm voltage setpoint and superimposed on the active current setpoint in a reverse droop manner. The arm voltage and the active current setpoint form a reverse droop relationship, that is:

[0156] I drefi =I dset -K VbI (V bset -V bi )

[0157] Among them, I drefi I is the reference value for the active current of the i-th power module; dset The active current setting is set to the same value for all modules or to zero; V bset The bridge arm voltage setting value is taken as the grid rated voltage. V bi K is the bridge arm voltage. VbI The active current-bridge arm voltage anti-droop coefficient is the active current reference value, which is a parameter reflecting the active current.

[0158] Then, the d-axis component of the bridge arm voltage is... With the active current reference value I dref The value after multiplication is the same as the q-axis component of the bridge arm voltage. With reactive current reference value I qref The multiplied values ​​are compared and used as the reference value i for the alternating current. gref To achieve closed-loop control, that is

[0159]

[0160] Among them, i gref I is the reference value for alternating current. dref I is the active current reference value. qref The reactive current reference value is; the bridge arm voltage is v bx For a sinusoidal fundamental signal in phase with the bridge arm voltage, v by For lag v bx A 90-degree sine wave signal.

[0161] The smaller the bridge arm voltage, the smaller the DC-Link voltage setpoint, i.e., the DC-Link voltage reference value. For scenarios where the DC-Link voltage is fixed, such as a battery voltage, sampling the aforementioned current loop control is sufficient, with the active current setpoint I... dset The active current setting can be set according to the system's required active current. For scenarios where the DC-link voltage is a capacitor and the DC load varies, the active current setting value I... dset It can be generated by the DC-link voltage outer loop.

[0162] like Figure 5 As shown, for scenarios requiring control of the DC-link voltage, this embodiment further proposes that the DC-link-bridge arm voltage adopt anti-droop control, superimposed on the reference value of the DC-link voltage, that is:

[0163] The bridge arm voltage V bi With bridge arm voltage setting value V bset In comparison, the voltage v is superimposed on the DC link voltage setpoint in the form of a reverse droop. dcset Control the DC link voltage reference value v dcrefi ,Right now:

[0164] v dcrefi =v dcset -K vb (V bset -V bi );

[0165] Among them, v dcrefi This is the reference value for the DC link voltage, v dcset This is the DC link voltage setting value. (V) bset This is the bridge arm voltage setting value, which can be taken as the grid rated voltage. V bi K is the bridge arm voltage. vb The anti-droop control factor is the bridge arm voltage V. bi The smaller the value, the lower the DC link voltage reference value v. dcrefi The smaller it is.

[0166] This application also provides a non-communication distributed control device for a cascaded system, wherein at least two power modules are cascaded to form a cascaded system, and each power module includes a control module, the control module being used for:

[0167] The output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value.

[0168] The bridge arm voltage is obtained by observing the bridge arm voltage reference value, and the bridge arm voltage is used as a feedback signal. After being jointly adjusted by the AC current of the power module through closed-loop control, the bridge arm voltage reference value is controlled.

[0169] Control the bridge arm voltage according to the bridge arm voltage reference value;

[0170] In at least one operating mode of the cascaded system, the change in the parameter reflecting the active current is monotonic with the change in the arm voltage.

[0171] Optionally, the arm voltage is obtained by observing the arm voltage reference value, and the arm voltage is used as a feedback signal. After passing through closed-loop control together with the AC current of the power module, the arm voltage reference value is controlled, including:

[0172] The arm voltage is compared with the arm voltage setpoint and superimposed on the active current setpoint in a reverse droop manner, i.e.:

[0173] I drefi =I dset -K VbI (V bset -V bi )

[0174] Among them, I drefi I is the active current reference value for the i-th power module. dset The active current setpoint, V bset V is the bridge arm voltage setting value. bi K is the bridge arm voltage. VbI The active current-bridge arm voltage anti-droop coefficient is the active current reference value, which is a parameter reflecting the active current.

[0175] Optionally, the value obtained by multiplying the d-axis component of the bridge arm voltage by the active current reference value, and then comparing it with the value obtained by multiplying the q-axis component of the bridge arm voltage by the reactive current reference value, is used as the AC current reference value.

[0176]

[0177] Among them, i gref I is the reference value for alternating current. drefI is the active current reference value. qref The reactive current reference value is; the bridge arm voltage is v bx For a sinusoidal fundamental signal in phase with the bridge arm voltage, v by For lag v bx A 90-degree sine wave signal.

[0178] Optionally, the output of the AC current of the power module after closed-loop control regulation is used as the bridge arm voltage reference value, including:

[0179] Sample alternating current;

[0180] The AC current reference value is compared with the AC current to generate a current error. After the current error is adjusted by the current regulator, the sinusoidal fundamental signal of the bridge arm voltage in phase is added as feedforward to obtain the bridge arm voltage reference value.

[0181] Optionally, the method of observing the bridge arm voltage reference value to obtain the bridge arm voltage, and using the bridge arm voltage as a feedback signal, together with the AC current of the power module, undergoes closed-loop control to control the bridge arm voltage reference value, including:

[0182] The bridge arm voltage was observed after the reference value of the bridge arm voltage was obtained by performing a second-order generalized integral.

[0183] Optionally, the control module is further configured to:

[0184] The arm voltage is compared with the arm voltage setpoint and superimposed on the DC link voltage setpoint in a reverse drooping manner, i.e.:

[0185] v dcrefi =v dcset -K vb (V bset -V bi );

[0186] Among them, v dcrefi This is the reference value for the DC link voltage, v dcset V is the DC link voltage setpoint. bset V is the bridge arm voltage setting value. bi K is the bridge arm voltage. vb This is the anti-droop control coefficient.

[0187] Optionally, the control module is further configured to:

[0188] When there is communication and coordination between the control modules of each power module, the DC link voltage setting value is compared with the DC link voltage to generate a DC link voltage error. The initial DC link voltage error of the other power module is used as a feedforward, coordinated and integrated, and then superimposed on the bridge arm voltage setting value.

[0189] The above description and accompanying drawings are merely examples of the technical concept of this disclosure. Those skilled in the art will understand that various modifications and variations in form, such as combinations, separations, substitutions, and changes of structures, can be made to the embodiments described herein without departing from the essential characteristics of this disclosure. Therefore, the embodiments disclosed in this disclosure are not intended to limit but rather describe the technical concept of this disclosure, and thus do not limit the scope of the technical concept of this disclosure. The scope of this disclosure should be interpreted based on the appended claims, and all technical concepts included within the scope of equivalents of the appended claims should be interpreted as including within the scope of this disclosure.

[0190] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A cascaded system communication-free distributed control method characterized by, At least two power modules are cascaded to form a cascade system, each of the power modules comprising a control module; the method comprises: The output of the AC current of the power module after closed-loop control adjustment is taken as a bridge arm voltage reference value; The bridge arm voltage is observed from the bridge arm voltage reference value, and the bridge arm voltage is taken as a feedback signal to control the bridge arm voltage reference value after closed-loop control adjustment of the AC current of the power module; The bridge arm voltage is controlled according to the bridge arm voltage reference value; In at least one working mode of the cascade system, the change of the parameter reflecting the active current and the change of the bridge arm voltage are in a monotonic relationship.

2. The method of claim 1, wherein, The bridge arm voltage is observed from the bridge arm voltage reference value, and the bridge arm voltage is taken as a feedback signal to control the bridge arm voltage reference value after closed-loop control of the AC current of the power module; The bridge arm voltage is compared with a bridge arm voltage set value to superimpose in the form of inverse droop on the active current set value to obtain the active current reference value, that is: I drefi = I dset - K VbI (V bset - V bi ) wherein I drefi is the active current reference value of the i-th power module, I dset is the active current setpoint, V bset is the bridge leg voltage setpoint, V bi is the bridge leg voltage, K VbI is the active current-bridge leg voltage inverse droop coefficient, the active current reference value being a parameter reflecting the active current.

3. The method of claim 2, wherein, The set value V of the bridge arm voltage bset is taken as the grid rated voltage.

4. The method of claim 2, wherein, The d-axis component of the bridge arm voltage is multiplied by the active current reference value, and the result is compared with the q-axis component of the bridge arm voltage multiplied by the reactive current reference value to obtain the AC current reference value, that is wherein, i gref is the AC current reference value, I dref is the active current reference value, I qref is the reactive current reference value; the bridge arm voltage is v bx is a sinusoidal fundamental signal in phase with the bridge arm voltage, v by is a sinusoidal signal 90 degrees out of phase with v bx 90 degrees.

5. The method of claim 4, wherein, The output of the AC current of the power module after closed-loop control adjustment is taken as a bridge arm voltage reference value, which comprises: The AC current is sampled; The AC current reference value is compared with the AC current to generate a current error, the bridge arm voltage reference value is obtained after the current error is adjusted by a current regulator and a sinusoidal fundamental wave signal in phase with the bridge arm voltage is added as feedforward.

6. The method of claim 1, wherein, The bridge arm voltage is observed from the bridge arm voltage reference value, and the bridge arm voltage is taken as a feedback signal to control the bridge arm voltage reference value after closed-loop control of the AC current of the power module; The bridge arm voltage reference value is observed after second-order generalized integration of the bridge arm voltage reference value.

7. The method of claim 1, wherein, The bridge arm voltage is compared with a bridge arm voltage set value to superimpose in the form of inverse droop on the DC link voltage set value, that is: The DC link voltage set value is compared with the DC link voltage to generate a DC link voltage error, and the initial DC link voltage error of another power module is taken as feedforward to be superimposed on the bridge arm voltage set value after coordination integration. v dcrefi = v dcset - K vb (V bset - V bi ); Wherein, v dcrefi is the DC link voltage reference value, v dcset is the DC link voltage set value, V bset is the bridge arm voltage set value, V bi is the bridge arm voltage, K vb is the inverse droop control coefficient.

8. The method of claim 7, wherein, The bridge arm voltages of the at least two power modules are the same. The power module comprises an AC-DC converter and a DC-DC converter, and the AC-DC converter is controlled by the distributed control method without communication of the cascade system.

9. The method of claim 8, wherein, The DC-DC converter is controlled by DC link voltage droop control or output current droop control.

10. The method according to any one of claims 1 to 9, characterized in that, The control in the DC-DC converter further comprises a secondary regulation loop.

11. The method of claim 10, wherein, Each single phase comprises at least one power module, each of the power modules comprising a control module; the method comprises:

12. The method of claim 11, wherein, At least two power modules are cascaded to form a cascade system, each of the power modules comprising a control module; the method comprises:

13. A communication-free distributed control method for a three-phase system, characterized by, ​ ​ The output of the closed-loop control of the AC current of the power module is taken as the bridge arm voltage reference value; The bridge arm voltage is observed from the bridge arm voltage reference value, and the bridge arm voltage is taken as a feedback signal to control the bridge arm voltage reference value through the closed-loop control of the AC current of the power module; The bridge arm voltage is controlled according to the bridge arm voltage reference value; In at least one working mode of the cascade system, the change of the parameter reflecting the active current and the change of the bridge arm voltage are in a monotonic relationship.

14. The method of claim 13, wherein, The bridge arm voltage is observed from the bridge arm voltage reference value, and the bridge arm voltage is taken as a feedback signal to control the bridge arm voltage reference value through the closed-loop control of the AC current of the power module; The bridge arm voltage is compared with the bridge arm voltage set value to obtain the active current reference value in the form of inverse droop superimposed on the active current set value, that is, I drefi = I dset - K VbI (V bset - V bi ) wherein I drefi is the active current reference value of the i-th power module, I dset is the active current setpoint, V bset is the bridge leg voltage setpoint, V bi is the bridge leg voltage, K VbI is the active current-bridge leg voltage inverse droop coefficient, the active current reference value being a parameter reflecting the active current.

15. The method of claim 14, wherein, The set value V of the bridge arm voltage bset is taken as the grid rated voltage.

16. The method of claim 15, wherein, The value obtained by multiplying the d-axis component of the bridge arm voltage by the active current reference value is compared with the value obtained by multiplying the q-axis component of the bridge arm voltage by the reactive current reference value to obtain the AC current reference value, that is wherein i gref is the AC current reference value, I dref is the active current reference value, I qref is the reactive current reference value; the bridge arm voltage is v bx is a sinusoidal fundamental signal in phase with the bridge arm voltage, v by is a sinusoidal signal 90 degrees behind v bx 90 degrees.

17. The method of claim 16, wherein, The output of the closed-loop control of the AC current of the power module is taken as the bridge arm voltage reference value, including: The AC current is sampled; The AC current reference value is compared with the AC current to generate a current error, and the bridge arm voltage reference value is obtained after the current error is adjusted by a current regulator and a sine wave signal in phase with the bridge arm voltage is added as feedforward.

18. The method of claim 13, wherein, The bridge arm voltage is observed from the bridge arm voltage reference value, and the bridge arm voltage is taken as a feedback signal to control the bridge arm voltage reference value through the closed-loop control of the AC current of the power module; The bridge arm voltage is observed from the bridge arm voltage reference value after the bridge arm voltage reference value is passed through a second-order generalized integral.

19. The method of claim 13, wherein, Further comprising: The bridge arm voltage is compared with the bridge arm voltage set value to obtain the active current reference value in the form of inverse droop superimposed on the DC link voltage set value, that is, v dcrefi = v dcset - K vb (V bset - V bi ); Wherein, v dcrefi is the DC link voltage reference value, v dcset is the DC link voltage set value, V bset is the bridge arm voltage set value, V bi is the bridge arm voltage, K vb is the inverse droop control coefficient.

20. The method of claim 19, wherein, Further comprising: In the case of communication coordination between the control modules of the power modules, a DC link voltage error is generated by comparing the DC link voltage set value with the DC link voltage, the initial DC link voltage error of another power module is taken as feedforward, and the bridge arm voltage set value is superimposed after integration.

21. The method of claim 20, wherein, The bridge arm voltages of the at least two power modules are the same.

22. The method of any of claims 13-21, wherein, The power module comprises an AC-DC converter and a DC-DC converter, and the AC-DC converter is controlled by using the cascade system communication-free distributed control method.

23. The method of claim 22, wherein, The DC-DC converter adopts DC link voltage droop control or output current droop control.

24. The method of claim 23, wherein, The control in the DC-DC converter further comprises a secondary regulation loop.

25. A cascading system non-communication distributed control device, characterized by, At least two power modules are cascaded to form a cascade system, and each power module comprises a control module, and the control module is used to: The output of the closed-loop control of the AC current of the power module is taken as the bridge arm voltage reference value; Observe the bridge arm voltage reference value to obtain the bridge arm voltage, and take the bridge arm voltage as a feedback signal, and control the bridge arm voltage reference value after the bridge arm voltage and the AC current of the power module are jointly adjusted through closed-loop control. Control the bridge arm voltage according to the bridge arm voltage reference value. In at least one working mode of the cascade system, the change of the parameter reflecting the active current and the change of the bridge arm voltage are in a monotonic relationship.

26. The apparatus of claim 25, wherein, The observation of the bridge arm voltage reference value to obtain the bridge arm voltage, and the control of the bridge arm voltage reference value after the bridge arm voltage is taken as a feedback signal and the AC current of the power module is jointly adjusted through closed-loop control, includes: The bridge arm voltage is compared with the bridge arm voltage set value to obtain the active current reference value in the form of anti-droop superimposed on the active current set value, that is: I drefi = I dset - K VbI (V bset - V bi ) wherein I drefi is the active current reference value of the i-th power module, I dset is the active current setpoint, V bset is the bridge leg voltage setpoint, V bi is the bridge leg voltage, K VbI is the active current-bridge leg voltage inverse droop coefficient, the active current reference value being a parameter reflecting the active current.

27. The apparatus of claim 26, wherein, The value obtained by multiplying the d-axis component of the bridge arm voltage by the active current reference value is compared with the value obtained by multiplying the q-axis component of the bridge arm voltage by the reactive current reference value, and the comparison result is taken as the AC current reference value, that is wherein i gref is the AC current reference value, I dref is the active current reference value, I qref is the reactive current reference value; the bridge arm voltage is v bx is a sinusoidal fundamental signal in phase with the bridge arm voltage, v by is a sinusoidal signal 90 degrees behind v bx 90 degrees.

28. The apparatus of claim 27, wherein, The output of the AC current of the power module after closed-loop control adjustment is taken as the bridge arm voltage reference value, including: Sample the AC current; The AC current reference value is compared with the AC current to generate a current error, and the bridge arm voltage reference value is obtained after the current error is adjusted by a current regulator and a sinusoidal fundamental signal in phase with the bridge arm voltage is added as feedforward.

29. The apparatus of claim 25, wherein, The observation of the bridge arm voltage reference value to obtain the bridge arm voltage, and the control of the bridge arm voltage reference value after the bridge arm voltage is taken as a feedback signal and the AC current of the power module is jointly adjusted through closed-loop control, includes: The bridge arm voltage is observed after the bridge arm voltage reference value is passed through a second-order generalized integral.

30. The apparatus of claim 25, wherein, The control module is further used for: The bridge arm voltage is compared with the bridge arm voltage set value to obtain the DC link voltage set value in the form of anti-droop superimposed on the DC link voltage set value, that is: v dcrefi = v dcset - K vb (V bset - V bi ); Wherein, v dcrefi is the DC link voltage reference value, v dcset is the DC link voltage set value, V bset is the bridge arm voltage set value, V bi is the bridge arm voltage, K vb is the inverse droop control coefficient.

31. The apparatus of claim 30, wherein, The control module is further used for: In the case of communication and coordination between the control modules of the power modules, the DC link voltage set value is compared with the DC link voltage to generate a DC link voltage error, the initial DC link voltage error of another power module is taken as feedforward, and the bridge arm voltage set value is superimposed after coordination and integration.

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