Capacitor voltage equalization control method, device and system

Abstract

The application discloses a capacitor voltage equalization control method, device and system. The method comprises the following steps: superimposing a voltage stabilizing control quantity on an active current loop at a DC side of a three-level H-bridge chain type dynamic reactive power compensation device; adjusting energy exchange between the three-level H-bridge chain type dynamic reactive power compensation device and a power grid according to the voltage stabilizing control quantity, so that total average voltage between multiple chain links is stable; adjusting active exchange between each chain link in a phase and between each chain link in a phase by superimposing two active voltage vectors which are perpendicular to each other respectively, so that DC voltage in the multiple chain links is balanced; and equalizing capacitor voltage at a power module DC side of the three-level H-bridge chain type dynamic reactive power compensation device. The application realizes active energy balance between a device and an AC power grid and between each chain link in the device.

Description

Technical Field

[0001] This application relates to the field of chain-type dynamic reactive power compensation technology, and in particular to a capacitor voltage equalization control method, device and system. Background Technology

[0002] Each phase of a chain-type dynamic reactive power compensation device (also known as a chain-type static synchronous compensation device) consists of multiple identical two-level H-bridge power modules connected in series. This topology is simple and easy to implement. However, under high grid voltage levels, the two-level H-bridge requires more power modules connected in series, increasing the size of the device and reducing the reliability of the system.

[0003] The chain-type dynamic reactive power compensation device based on a three-level H-bridge requires fewer power modules in series under the same voltage level and switching transistors, resulting in a smaller device size and reduced complexity of the control system. However, the imbalance of DC-side capacitor voltage in the chain-type dynamic reactive power compensation device based on the three-level H-bridge increases the degree of control freedom and makes DC-side capacitor voltage balancing control more difficult. Therefore, devices using this topology have not been widely used.

[0004] If a new dynamic capacitor voltage balance control method can be adopted on the DC side of the three-level H-bridge chain dynamic reactive power compensation device, the capacitor voltage balance can be achieved by controlling the capacitor current. Summary of the Invention

[0005] This application provides a capacitor voltage balancing control method, apparatus, and system to achieve capacitor voltage balancing by controlling capacitor current.

[0006] The embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, embodiments of this application provide a capacitor voltage equalization control method, wherein the method includes:

[0008] The active current loop on the DC side of the three-level H-bridge chain-type dynamic reactive power compensation device is superimposed with voltage regulation control quantity.

[0009] The energy exchange between the three-level H-bridge chain dynamic reactive power compensation device and the power grid is adjusted according to the voltage regulation control quantity so as to stabilize the total average voltage among multiple chain links.

[0010] By superimposing two mutually perpendicular active voltage vectors, the active power exchange between phase-to-phase and intra-phase links is adjusted to balance the DC voltage among the multiple links; and

[0011] The capacitor voltage on the DC side of the power module of the three-level H-bridge chain dynamic reactive power compensation device is balanced.

[0012] In some embodiments, adjusting the active power exchange between interphase and intraphase links by superimposing two mutually perpendicular active power voltage vectors to balance the DC voltage among the multiple links includes:

[0013] A phase-to-phase voltage balance control method is adopted to control the balance of the average capacitor voltage of each phase commutation link;

[0014] An intra-phase voltage balance control method is adopted to control the balance of capacitor voltages between links within each phase converter chain.

[0015] In some embodiments, the method further includes:

[0016] A DC-side neutral point voltage balance control method is adopted to control the voltage balance between the upper and lower capacitors.

[0017] In some embodiments, adjusting the active power exchange between interphase and intraphase links by superimposing two mutually perpendicular active power voltage vectors to balance the DC voltage among the multiple links includes:

[0018] Based on the phase-to-phase voltage balance control command, the average DC-side voltage of each link in the three-phase converter chain is generated;

[0019] Based on the average DC-side voltage of each link in the three-phase converter chain, the interphase voltage balance control quantity is obtained;

[0020] The phase-to-phase voltage balance control quantity is superimposed with the three-phase output control quantity of the current loop to achieve phase-to-phase DC voltage balance.

[0021] In some embodiments, the interphase voltage balance control quantities superimposed on each link within the same phase are the same, and the interphase voltage balance control quantities are voltage vectors that are in phase or out of phase with the output voltage vector of the link.

[0022] In some embodiments, the step of adjusting the active power exchange between phase-to-phase and intra-phase links by superimposing two mutually perpendicular active power voltage vectors to balance the DC voltage among the plurality of links further includes:

[0023] The average value of the DC-side capacitor voltage of each link in the phase is used as the control command.

[0024] According to the control command, the DC-side capacitor voltage of each link is fed back and compared with the average value of the DC-side capacitor voltage of each link in the phase to obtain the tracking error;

[0025] Based on the tracking error, the voltage balance control quantity within each link phase is obtained to balance the DC voltage among the multiple links.

[0026] In some embodiments, balancing the DC-side capacitor voltage of the power module of the three-level H-bridge chain-type dynamic reactive power compensation device includes:

[0027] If the voltage of the upper capacitor is greater than the voltage of the lower capacitor, the output DC regulation is positive, so that the output current contains a positive DC component.

[0028] If the voltage of the upper capacitor is less than the voltage of the lower capacitor, the output DC regulation is negative, so that the output current contains a negative DC component.

[0029] The capacitor voltage on the DC side of the power module is balanced based on the positive DC component and the negative DC component.

[0030] Secondly, embodiments of this application also provide a capacitor voltage equalization control device, wherein the device includes:

[0031] The overall voltage regulation control module is used to superimpose a voltage regulation control quantity on the active current loop of the DC side of the three-level H-bridge chain dynamic reactive power compensation device, and adjust the energy exchange between the three-level H-bridge chain dynamic reactive power compensation device and the power grid according to the voltage regulation control quantity, so as to stabilize the total average voltage between multiple chain links.

[0032] The phase-to-phase and intra-phase voltage balance control module is used to adjust the active power exchange between phase-to-phase and intra-phase links by superimposing two mutually perpendicular active power voltage vectors, so as to balance the DC voltage among the multiple links; and

[0033] The DC-side neutral point voltage balance control module is used to balance the capacitor voltage on the DC side of the power module of the three-level H-bridge chain dynamic reactive power compensation device.

[0034] Thirdly, embodiments of this application also provide a capacitor voltage balancing control system, wherein the system includes: a three-level H-bridge chain-type dynamic reactive power compensation device, an overall voltage regulation control module, an inter-phase DC voltage balancing control strategy module, an intra-phase DC voltage balancing control strategy module, and a DC-side midpoint voltage balancing control strategy module. Through the overall voltage regulation control module, the inter-phase DC voltage balancing control strategy module, the intra-phase DC voltage balancing control strategy module, and the DC-side midpoint voltage balancing control strategy module, the above-mentioned capacitor voltage balancing control method is used to balance and control the DC-side capacitor voltage.

[0035] Fourthly, embodiments of this application also provide a computer-readable storage medium that stores one or more programs, which, when executed by an electronic device including multiple applications, cause the electronic device to perform the above-described method.

[0036] The at least one technical solution adopted in this application embodiment can achieve the following beneficial effects: A voltage regulation control quantity is superimposed on the active current loop of the three-level H-bridge chain dynamic reactive power compensation device; the energy exchange between the three-level H-bridge chain dynamic reactive power compensation device and the power grid is adjusted according to the voltage regulation control quantity to stabilize the overall average voltage between multiple links, thus serving as an overall voltage regulation control strategy. By superimposing two mutually perpendicular active voltage vectors, the active power exchange between links between phases and within a phase is adjusted to balance the DC voltage among multiple links, thus serving as an inter-phase and intra-phase voltage balance control strategy. Finally, the capacitor voltage on the DC side of the power module of the three-level H-bridge chain dynamic reactive power compensation device is balanced as a DC side neutral point voltage balance control strategy. Through coordinated control of different strategies, a balance control algorithm is superimposed on current control to achieve DC side capacitor voltage balance. Attached Figure Description

[0037] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0038] Figure 1 This is a schematic diagram of a three-level H-bridge circuit in an embodiment of this application;

[0039] Figure 2 This is a diagram of the DC-side capacitor voltage equalization control structure of the three-level H-bridge dynamic reactive power compensation device in the embodiments of this application;

[0040] Figure 3 This is a diagram of the phase-to-phase voltage balance control structure in an embodiment of this application;

[0041] Figure 4 This is a diagram of the phase voltage balance control structure in an embodiment of this application;

[0042] Figure 5 This is a diagram of the DC-side neutral point voltage balance control structure in an embodiment of this application;

[0043] Figure 6 This is a schematic diagram of the capacitor voltage equalization control method in the embodiments of this application;

[0044] Figure 7 This is a schematic diagram of the capacitor voltage equalization control device in the embodiments of this application. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] During their research, the inventors discovered that the stability and balance of the DC-side capacitor voltages of each H-bridge power module in a chain-type dynamic reactive power compensation device are prerequisites for the device's normal operation. Because each DC-side capacitor is independent and involves series, parallel, and switching losses, differences in device parameters and inconsistent switching states can all lead to fluctuations and imbalances in the DC-side capacitor voltages. This adversely affects the normal operation and compensation performance of the chain-type dynamic reactive power compensation device. Voltage imbalance increases the harmonic distortion rate of the output voltage. When the imbalance is significant, the capacitor voltages of some power modules may be too high, affecting the safe operation of the device and reducing its compensation capability. Therefore, it is necessary to stably control the balance of the DC-side capacitor voltages.

[0047] In related technologies, commonly used control methods can be summarized into two categories: hardware voltage equalization and software voltage equalization.

[0048] (1) The hardware voltage equalization method uses an external balance control circuit to achieve dynamic balance of capacitor voltage. For example, the invention patent "Static Synchronous Compensator and Voltage Source Inverter Module Based on Three-Level H-Bridge Cascade" authorized by Shanghai Jiao Tong University proposes a hardware circuit for the DC-side capacitor voltage discharge circuit to complete the capacitor discharge when the DC-side capacitor voltage is too high or unbalanced.

[0049] (2) The software voltage equalization method does not require external hardware circuits. It achieves DC-side capacitor voltage balance by superimposing a balance control algorithm on current control. Since the uneven distribution of capacity and loss caused by the differences in hardware parameters between power modules is the direct cause of capacitor voltage imbalance, voltage balance control can be achieved by adjusting the energy exchange between the device and the grid, as well as the energy flow between the power modules.

[0050] However, the basic idea of ​​existing DC-side capacitor voltage balance control algorithms is to adopt hierarchical control. The upper-level control uses methods such as decoupling control and instantaneous current tracking to achieve the stability of the total DC voltage and the control of reactive power and harmonics in the system. The lower level uses balance control to achieve the distribution of energy between the three phases and between power modules in the same phase, so as to ensure the balance of DC capacitor voltage.

[0051] In the above scheme, although the hardware voltage equalization method has a better voltage equalization effect, it requires additional hardware circuits, which makes the system hardware structure more complex, reduces the reliability of the device, and increases the cost of the device.

[0052] While software methods do not require additional hardware circuits, they are all based on the DC-side capacitor voltage equalization control of a two-level H-bridge chain dynamic reactive power compensation device. Currently, no literature proposes a method for DC-side capacitor voltage equalization control based on a three-level H-bridge chain dynamic reactive power compensation device.

[0053] To address the aforementioned shortcomings, a dynamic balance control method for DC-side capacitor voltage based on a three-level H-bridge chain dynamic reactive power compensation device is proposed. This method achieves capacitor voltage balance by controlling the capacitor current.

[0054] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.

[0055] like Figure 1 The diagram shows the circuit schematic of a power module based on a three-level H-bridge chain-type dynamic reactive power compensation device. Under the same voltage level and switching transistors, the three-level H-bridge-based chain-type dynamic reactive power compensation device requires fewer power modules connected in series, resulting in a smaller device size and reduced complexity of the control system. However, the imbalance of the DC-side capacitor voltage in the three-level H-bridge-based chain-type dynamic reactive power compensation device increases the degree of control freedom, making DC-side capacitor voltage balancing control more difficult. Therefore, devices using this topology have not been widely adopted.

[0056] like Figure 2 The diagram shown is a schematic of the DC-side capacitor voltage balancing control structure of a three-level H-bridge dynamic reactive power compensation device. The DC-side capacitor voltage balancing control is divided into:

[0057] Overall voltage stabilization control, phase-to-phase voltage balance control, phase-to-phase voltage balance control, and DC-side neutral point voltage balance control respectively achieve functional energy balance between the device and the AC grid, and between various links within the device.

[0058] Please continue to refer to this. Figure 2 The overall voltage regulation control includes: adjusting the energy exchange between the device and the power grid by superimposing voltage regulation control quantity on the active current loop, so as to achieve the stability of the total average voltage of each link.

[0059] like Figure 3 as well as Figure 4 As shown, phase-to-phase and intra-phase voltage balance control includes: superimposing two mutually perpendicular active voltage vectors U... Ba,b,c and Δu ki(k = a, b, c; i = 1, 2, ..., N) Adjust the active power exchange between phases and between links within a phase to achieve the balance of DC voltage in each link. The subscripts i = 1, 2, ..., N in the figure are the link numbers in each phase.

[0060] like Figure 5 As shown, the DC-side neutral point voltage balance control is used to balance the voltage of the upper and lower independent capacitors on the DC side of the three-level H-bridge power module.

[0061] Please refer to Figure 2 middle N is the number of links in each phase. V dc_ref U is the total reference voltage for the DC-side capacitors of each power module. dc_ki (k = a, b, c; i = 1, 2, ..., N) represents the actual voltage of the DC-side capacitor of each power module in each phase.

[0062] Please refer to Figure 3 middle U dck (k = a, b, c) is the sum of the actual voltages of the DC-side capacitors of each power module in each phase.

[0063] Please refer to Figure 4 middle It is the average value of the DC-side capacitor voltage of the power module for each phase.

[0064] This application provides a capacitor voltage equalization control method, such as... Figure 6 The diagram shows a flowchart of a capacitor voltage equalization control method in an embodiment of this application. The method includes at least the following steps S610 to S640:

[0065] Step S610: The active current loop on the DC side of the three-level H-bridge chain-type dynamic reactive power compensation device is superimposed with the voltage regulation control quantity.

[0066] Step S620: Adjust the energy exchange between the three-level H-bridge chain dynamic reactive power compensation device and the power grid according to the voltage regulation control quantity, so as to stabilize the total average voltage between multiple chain links.

[0067] By superimposing voltage regulation control on the active current loop on the DC side of the three-level H-bridge chain-type dynamic reactive power compensation device, the energy exchange between the device and the power grid is regulated, thereby stabilizing the total average voltage of each chain link.

[0068] Step S630: By superimposing two mutually perpendicular active voltage vectors, the active power exchange between phases and between each link in the phase is adjusted so as to balance the DC voltage among the multiple links.

[0069] The interphase voltage balance control method is adopted to control the balance of the average capacitor voltage of each phase commutator chain. That is, the interphase voltage balance control objective is to balance the average capacitor voltage of each phase commutator chain.

[0070] The intra-phase voltage balance control method is adopted to control the balance of capacitor voltage between each link in the converter chain within each phase. That is, the intra-phase voltage balance control objective is to balance the capacitor voltage between each link in the converter chain within each phase.

[0071] Step S640: Equalize the capacitor voltage on the DC side of the power module of the three-level H-bridge chain dynamic reactive power compensation device.

[0072] The DC-side neutral point voltage balance control is used to balance the voltage of the two independent capacitors on the DC side of the three-level H-bridge power module.

[0073] In some embodiments, adjusting the active power exchange between interphase and intraphase links by superimposing two mutually perpendicular active power voltage vectors to balance the DC voltage among the multiple links includes: using an interphase voltage balance control method to control the balance of the average capacitor voltage of each phase converter chain; and using an intraphase voltage balance control method to control the balance of capacitor voltage among the links within each phase converter chain.

[0074] In some embodiments, the method further includes: using a DC-side neutral point voltage balance control method to control the balance of voltage between the upper and lower capacitors.

[0075] In one embodiment of this application, the step of adjusting the active power exchange between interphase and intraphase links by superimposing two mutually perpendicular active power voltage vectors to balance the DC voltage among the multiple links includes: generating the average DC-side voltage of each link in the three-phase converter chain according to the interphase voltage balance control command; obtaining the interphase voltage balance control quantity according to the average DC-side voltage of each link in the three-phase converter chain; and superimposing the interphase voltage balance control quantity with the three-phase output control quantity of the current loop to achieve interphase DC voltage balance.

[0076] like Figure 3 As shown, the phase-to-phase voltage balance control objective is to balance the average value of the capacitor voltages in each phase commutator chain. The control strategy is as follows: Figure 3 As shown. Where U dcav For phase-to-phase voltage balance control command, U dca,b,c These represent the average DC-side voltages of each link in the three-phase converter chain. The active power absorbed by the three-phase converter chain is adjusted through feedback active current. Proportional controllers K1 and K2 multiply the controller outputs by the sinusoidal values ​​of the phase voltage phase corresponding to the PCC point output of the phase-locked loop, converting them into fundamental AC quantities to obtain the inter-phase voltage balance control quantity U. Ba,b,c balance control quantity and Figure 2Medium current loop three-phase output control quantity U Aa,b,c The superposition achieves phase-to-phase voltage balance.

[0077] Preferably, the interphase voltage balance control quantities superimposed on each link within the same phase are the same, and the interphase voltage balance control quantities are voltage vectors that are in phase or out of phase with the output voltage vector of the link.

[0078] In one embodiment of this application, the step of adjusting the active power exchange between phases and between links within a phase by superimposing two mutually perpendicular active power voltage vectors to balance the DC voltage among the multiple links further includes: using the average value of the DC-side capacitor voltage of each link within the phase as a control command for each phase; feeding back the DC-side capacitor voltage of each link according to the control command and comparing it with the average value of the DC-side capacitor voltage of each link within the phase to obtain a tracking error; and obtaining the voltage balance control amount within each link based on the tracking error to balance the DC voltage among the multiple links.

[0079] like Figure 4 As shown, the phase-to-phase voltage balance control method aims to balance the capacitor voltages between links within each phase converter chain. The average DC-side capacitor voltage U of each link within the phase is used as the control metric. dc_mk (k = a, b, c) represents the control commands, and the control strategy is as follows: Figure 4 As shown. Feedback DC-side capacitor voltage U of each link. dc_ci (i = 1, 2, ..., N) and the corresponding phase voltage command U dc_mk The tracking error is obtained by comparing (k = a, b, c). This error is then adjusted using a proportional controller. The controller's output adjustment is multiplied by the cosine of the phase voltage phase corresponding to the public grid connection point output by the phase-locked loop, converting it into a fundamental AC quantity. This yields the voltage balance control quantity Δu within each link phase. ki (k = a, b, c; i = 1, 2, ..., N), the sign of the balance control quantity is determined based on the nature of the reactive power compensation current. When the device is in capacitive operation, the output current I... cq >0, sign is positive, when the device is in inductive operation, the output current I cq <0, the sign is negative.

[0080] In one embodiment of this application, balancing the capacitor voltage on the DC side of the power module of the three-level H-bridge chain dynamic reactive power compensation device includes: if the upper capacitor voltage is greater than the lower capacitor voltage, the output DC regulation is positive so that the output current contains a positive DC component; if the upper capacitor voltage is less than the lower capacitor voltage, the output DC regulation is negative so that the output current contains a negative DC component; and balancing the capacitor voltage on the DC side of the power module according to the positive DC component and the negative DC component.

[0081] like Figure 5As shown, the DC-side neutral point voltage balance control works when the voltages of the upper and lower capacitors become unbalanced, such as when the upper capacitor voltage U... dc1 Greater than the lower capacitor voltage U dc2 At that time, through the action of the PI regulator in the voltage equalization control loop, the output DC regulation quantity Δi is obtained. d When the value is positive, under the influence of this active current, the output current will contain a positive DC component. This positive DC component will cause the average voltage of the upper capacitor to decrease while the average voltage of the lower capacitor increases, thus making the current and the output current tend to be equal. Conversely, when the voltage of the upper capacitor U is negative... dc1 Less than the lower capacitor voltage U dc2 At that time, the output adjustment amount Δi d If the value is negative, the output current will contain a negative DC component. The effect of the negative DC component will cause the average voltage of the upper capacitor to rise and the average voltage of the lower capacitor to fall, eventually bringing the voltages of the upper and lower capacitors to a balance.

[0082] This application embodiment also provides a capacitor voltage equalization control device 700, such as... Figure 7 As shown, a schematic diagram of the capacitor voltage balancing control device in this application embodiment is provided. The capacitor voltage balancing control device 700 includes at least: an overall voltage regulation control module 710, a phase-to-phase and phase-to-phase DC voltage balancing control module 720, and a DC-side neutral point voltage balancing control module 730, wherein:

[0083] In one embodiment of this application, the acquisition module 710 is specifically used to: superimpose a voltage regulation control quantity onto the active current loop on the DC side of the three-level H-bridge chain dynamic reactive power compensation device, and adjust the energy exchange between the three-level H-bridge chain dynamic reactive power compensation device and the power grid according to the voltage regulation control quantity, so as to stabilize the total average voltage between multiple chain links.

[0084] By superimposing voltage regulation control on the active current loop on the DC side of the three-level H-bridge chain-type dynamic reactive power compensation device, the energy exchange between the device and the power grid is regulated, thereby stabilizing the total average voltage of each chain link.

[0085] In one embodiment of this application, the phase-to-phase and intra-phase DC voltage balance control module 720 is specifically used to: adjust the active power exchange between each link in the phase-to-phase and intra-phase by superimposing two mutually perpendicular active power voltage vectors, so as to balance the DC voltage among the multiple links.

[0086] The interphase voltage balance control method is adopted to control the balance of the average capacitor voltage of each phase commutator chain. That is, the interphase voltage balance control objective is to balance the average capacitor voltage of each phase commutator chain.

[0087] The intra-phase voltage balance control method is adopted to control the balance of capacitor voltage between each link in the converter chain within each phase. That is, the intra-phase voltage balance control objective is to balance the capacitor voltage between each link in the converter chain within each phase.

[0088] In one embodiment of this application, the DC-side neutral point voltage balance control module 730 is specifically used to: balance the capacitor voltage on the DC side of the power module of the three-level H-bridge chain dynamic reactive power compensation device.

[0089] The DC-side neutral point voltage balance control is used to balance the voltage of the two independent capacitors on the DC side of the three-level H-bridge power module.

[0090] In some embodiments, adjusting the active power exchange between interphase and intraphase links by superimposing two mutually perpendicular active power voltage vectors to balance the DC voltage among the multiple links includes: using an interphase voltage balance control method to control the balance of the average capacitor voltage of each phase converter chain; and using an intraphase voltage balance control method to control the balance of capacitor voltage among the links within each phase converter chain.

[0091] In some embodiments, the method further includes: using a DC-side neutral point voltage balance control method to control the balance of voltage between the upper and lower capacitors.

[0092] It is understood that the above-mentioned capacitor voltage equalization control device can realize each step of the capacitor voltage equalization control method provided in the foregoing embodiments. The relevant explanations of the capacitor voltage equalization control method are applicable to the capacitor voltage equalization control device, and will not be repeated here.

[0093] This application also proposes a capacitor voltage balancing control system, wherein the system includes: a three-level H-bridge chain-type dynamic reactive power compensation device, an overall voltage regulation control module, an inter-phase DC voltage balancing control strategy module, an intra-phase DC voltage balancing control strategy module, and a DC side midpoint voltage balancing control strategy module.

[0094] The capacitor voltage on the DC side is balanced using the overall voltage regulation control module, the inter-phase DC voltage equalization control strategy module, the intra-phase DC voltage equalization control strategy module, and the DC side midpoint voltage balance control strategy module, employing the capacitor voltage equalization control method described above.

[0095] The specific control method includes superimposing a voltage regulation control quantity on the active current loop of the three-level H-bridge chain dynamic reactive power compensation device; adjusting the energy exchange between the three-level H-bridge chain dynamic reactive power compensation device and the power grid according to the voltage regulation control quantity to stabilize the total average voltage between multiple links; adjusting the active power exchange between links between phases and within a phase by superimposing two mutually perpendicular active voltage vectors to balance the DC voltage among the multiple links; and balancing the capacitor voltage on the DC side of the power module of the three-level H-bridge chain dynamic reactive power compensation device.

[0096] Compared to the hardware-based equalization method for DC-side capacitor voltage (i.e., using additional hardware circuitry to control the discharge of the upper and lower capacitors on the DC side of the three-level H-bridge power module), the method in this application embodiment achieves DC-side capacitor voltage balance by superimposing a balance control algorithm on current control in software without adding or removing additional hardware circuitry.

[0097] Compared to the two-level H-bridge dynamic reactive power compensation device in related technologies, the research object in this application embodiment is a three-level H-bridge power module with upper and lower capacitors on its DC side. This increases the degree of control freedom, thereby increasing the difficulty of controlling the DC side capacitor voltage. In order to stably and reliably control the DC side capacitor voltage, this application embodiment adds a DC side neutral point voltage balance control method.

[0098] This application also proposes a computer-readable storage medium that stores one or more programs, the programs including instructions that, when executed by an electronic device including multiple applications, enable the electronic device to perform... Figure 6 The method executed by the capacitor voltage equalization control device in the illustrated embodiment is specifically used to perform the following:

[0099] The active current loop on the DC side of the three-level H-bridge chain-type dynamic reactive power compensation device is superimposed with voltage regulation control quantity.

[0100] The energy exchange between the three-level H-bridge chain dynamic reactive power compensation device and the power grid is adjusted according to the voltage regulation control quantity so as to stabilize the total average voltage among multiple chain links.

[0101] By superimposing two mutually perpendicular active voltage vectors, the active power exchange between phase-to-phase and intra-phase links is adjusted to balance the DC voltage among the multiple links; and

[0102] The capacitor voltage on the DC side of the power module of the three-level H-bridge chain dynamic reactive power compensation device is balanced.

[0103] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0104] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A capacitor voltage equalization control method, wherein, The method includes: The active current loop on the DC side of the three-level H-bridge chain-type dynamic reactive power compensation device is superimposed with voltage regulation control quantity. The energy exchange between the three-level H-bridge chain dynamic reactive power compensation device and the power grid is adjusted according to the voltage regulation control quantity so as to stabilize the total average voltage among multiple chain links. By superimposing two mutually perpendicular active voltage vectors, the active power exchange between phase-to-phase and intra-phase links is adjusted to balance the DC voltage among the multiple links; and Equalize the DC-side capacitor voltage of the power module of the three-level H-bridge chain dynamic reactive power compensation device; The method of adjusting the active power exchange between phase-to-phase and intra-phase links by superimposing two mutually perpendicular active voltage vectors to balance the DC voltage among the multiple links further includes: The average value of the DC-side capacitor voltage of each link in the phase is used as the control command. According to the control command, the DC-side capacitor voltage of each link is fed back and compared with the average value of the DC-side capacitor voltage of each link in the phase to obtain the tracking error; Based on the tracking error, the voltage balance control quantity within each link phase is obtained to balance the DC voltage among the multiple links.

2. The method as described in claim 1, wherein, The method of adjusting the active power exchange between phase-to-phase and intra-phase links by superimposing two mutually perpendicular active voltage vectors to balance the DC voltage among the multiple links includes: A phase-to-phase voltage balance control method is adopted to control the balance of the average capacitor voltage of each phase commutation link; An intra-phase voltage balance control method is adopted to control the balance of capacitor voltages between links within each phase converter chain.

3. The method as described in claim 2, wherein, The method further includes: A DC-side neutral point voltage balance control method is adopted to control the voltage balance between the upper and lower capacitors.

4. The method as described in claim 1, wherein, The method of adjusting the active power exchange between phase-to-phase and intra-phase links by superimposing two mutually perpendicular active voltage vectors to balance the DC voltage among the multiple links includes: Based on the phase-to-phase voltage balance control command, the average DC-side voltage of each link in the three-phase converter chain is generated; Based on the average DC-side voltage of each link in the three-phase converter chain, the interphase voltage balance control quantity is obtained; The phase-to-phase voltage balance control quantity is superimposed with the three-phase output control quantity of the current loop to achieve phase-to-phase DC voltage balance.

5. The method as described in claim 4, wherein, The interphase voltage balance control quantities superimposed on each link within the same phase are the same, and the interphase voltage balance control quantities are voltage vectors that are in phase or out of phase with the output voltage vector of the link.

6. The method of claim 1, wherein, The equalization of the DC-side capacitor voltage of the power module of the three-level H-bridge chain-type dynamic reactive power compensation device includes: If the voltage of the upper capacitor is greater than the voltage of the lower capacitor, the output DC regulation is positive, so that the output current contains a positive DC component. If the voltage of the upper capacitor is less than the voltage of the lower capacitor, the output DC regulation is negative, so that the output current contains a negative DC component. The capacitor voltage on the DC side of the power module is balanced based on the positive DC component and the negative DC component.

7. A capacitor voltage equalization control device, wherein, The device includes: The overall voltage regulation control module is used to superimpose a voltage regulation control quantity on the active current loop of the DC side of the three-level H-bridge chain dynamic reactive power compensation device, and adjust the energy exchange between the three-level H-bridge chain dynamic reactive power compensation device and the power grid according to the voltage regulation control quantity, so as to stabilize the total average voltage between multiple chain links. The phase-to-phase and intra-phase DC voltage balance control module is used to adjust the active power exchange between each link in the phase-to-phase and intra-phase links by superimposing two mutually perpendicular active power voltage vectors, so as to balance the DC voltage among the multiple links; and The DC-side neutral point voltage balance control module is used to balance the capacitor voltage on the DC side of the power module of the three-level H-bridge chain dynamic reactive power compensation device. The method of adjusting the active power exchange between phase-to-phase and intra-phase links by superimposing two mutually perpendicular active voltage vectors to balance the DC voltage among the multiple links further includes: The average value of the DC-side capacitor voltage of each link in the phase is used as the control command. According to the control command, the DC-side capacitor voltage of each link is fed back and compared with the average value of the DC-side capacitor voltage of each link in the phase to obtain the tracking error; Based on the tracking error, the voltage balance control quantity within each link phase is obtained to balance the DC voltage among the multiple links.

8. A capacitor voltage equalization control system, wherein, The system includes: a three-level H-bridge chain-type dynamic reactive power compensation device, an overall voltage regulation control module, an inter-phase DC voltage balancing control strategy module, an intra-phase DC voltage balancing control strategy module, and a DC side midpoint voltage balancing control strategy module. The capacitor voltage on the DC side is balanced using the overall voltage regulation control module, the inter-phase DC voltage equalization control strategy module, the intra-phase DC voltage equalization control strategy module, and the DC side midpoint voltage balance control strategy module, employing the capacitor voltage equalization control method as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing one or more programs, which, when executed by an electronic device including a plurality of applications, cause the electronic device to perform the method of any one of claims 1 to 6.

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