Power quality regulation device and method

Abstract

The present invention discloses a power quality regulation device and method, which relates to the field of power quality management technology. The device includes a low-frequency module, a high-frequency module, a neutral point clamping module, a first switching module, and a second switching module. The output port of the low-frequency module is connected to one end of the first switching module, and the output port of the high-frequency module is connected to one end of the second switching module. The other end of the first switching module and the other end of the second switching module are connected to the power grid via a coupling transformer. The output port of the neutral point clamping module is connected to the power grid via a filter. The first end of the neutral point clamping module is connected to the first end of the low-frequency module and the first end of the high-frequency module respectively. The second end of the neutral point clamping module is connected to the second end of the low-frequency module and the second end of the high-frequency module respectively. The third end of the neutral point clamping module is connected to the third end of the low-frequency module. The device solves the technical problem that the power density of existing power quality regulators is low, which reduces the reliability of distribution network operation.

Description

Technical Field

[0001] The present invention relates to the technical field of power quality management, and in particular to a power quality regulation device and method. Background Art

[0002] In recent years, with the rapid development of power electronics technology and the increase in nonlinear loads such as renewable energy, energy storage, and electric vehicles, power grids are facing serious power quality issues such as voltage sags, voltage swells, harmonics, reactive power, and three-phase imbalance. To address these power quality issues, many series / parallel power quality control devices have been developed, such as static VAR generators (SVGs) and dynamic voltage restorers (DVRs). However, these devices can only address voltage or current-related power quality issues and are unable to comprehensively address both voltage and current-related issues in the distribution network.

[0003] At present, the existing technology mainly uses a unified power quality conditioner (UPQC) to comprehensively manage voltage and current problems in the distribution network. However, due to the voltage resistance, current flow level and physical limits of semiconductor power devices, it is difficult to further improve the power density of the unified power quality conditioner, which reduces the reliability of the distribution network operation. Summary of the Invention

[0004] The present invention provides a power quality regulation device and method, which solves the technical problem that the existing technology mainly uses a unified power quality conditioner to comprehensively manage voltage and current problems in the distribution network, but is limited by the voltage resistance, current flow level and physical limits of semiconductor power devices, making it difficult to further improve the power density of the unified power quality conditioner, thereby reducing the reliability of the distribution network operation.

[0005] A first aspect of the present invention provides a power quality adjustment device, comprising a low-frequency module, a high-frequency module, a neutral point clamping module, a first switching module and a second switching module;

[0006] The output port of the low-frequency module is connected to one end of the first switching module, and the output port of the high-frequency module is connected to one end of the second switching module;

[0007] The other end of the first switching module and the other end of the second switching module are connected to the power grid through a coupling transformer;

[0008] The output port of the neutral point clamping module is connected to the power grid through a filter, and the first end of the neutral point clamping module is connected to the first end of the low frequency module and the first end of the high frequency module respectively;

[0009] The second end of the neutral point clamping module is connected to the second end of the low-frequency module and the second end of the high-frequency module respectively;

[0010] The third end of the neutral point clamping module is connected to the third end of the low-frequency module.

[0011] Optionally, the neutral point clamping module includes a single-phase neutral point clamping unit, a first capacitor and a second capacitor;

[0012] The first end of the single-phase neutral point clamping unit is connected to the positive electrode of the first capacitor, and the positive electrode of the first capacitor serves as the first end of the neutral point clamping module;

[0013] The second end of the single-phase neutral point clamping unit is connected to the negative electrode of the second capacitor, and the negative electrode of the second capacitor serves as the second end of the neutral point clamping module;

[0014] The third end of the single-phase neutral point clamping unit is connected to the negative electrode of the first capacitor and the positive electrode of the second capacitor respectively, and the third end of the single-phase neutral point clamping unit serves as the third end of the neutral point clamping module;

[0015] The output port of the single-phase neutral point is connected to the power grid through the filter.

[0016] Optionally, the single-phase neutral point clamping unit includes a first IGBT module, a second IGBT module, a third IGBT module, a fourth IGBT module, a first diode and a second diode;

[0017] The emitter of the first IGBT module is connected to the collector of the second IGBT module and the cathode of the first diode respectively, and the collector of the first IGBT module serves as the first end of the single-phase neutral point clamping unit;

[0018] The emitter of the second IGBT module is connected to the collector of the third IGBT module and one end of the filter respectively;

[0019] The anode of the first diode serves as the third terminal of the single-phase neutral point clamping unit;

[0020] The emitter of the third IGBT module is connected to the collector of the fourth IGBT module and the anode of the second diode respectively, and the emitter of the fourth IGBT module serves as the second end of the single-phase neutral point clamping unit;

[0021] The anode of the first diode is connected to the cathode of the second diode.

[0022] Optionally, the low-frequency module includes a fifth IGBT module, a sixth IGBT module, a seventh IGBT module, an eighth IGBT module, a third diode and a fourth diode;

[0023] The emitter of the fifth IGBT module is connected to the collector of the sixth IGBT module and the cathode of the third diode respectively, and the collector of the fifth IGBT module serves as the first end of the low-frequency module;

[0024] The emitter of the sixth IGBT module is connected to the collector of the seventh IGBT module and one end of the first switching module respectively;

[0025] The emitter of the seventh IGBT module is connected to the collector of the eighth IGBT module and the anode of the fourth diode respectively, and the emitter of the eighth IGBT module serves as the second end of the low-frequency module;

[0026] The anode of the third diode is connected to the cathode of the fourth diode, and the anodes of the three diodes serve as the third end of the low-frequency module.

[0027] Optionally, the high-frequency module includes a first wide-bandgap semiconductor device and a second wide-bandgap semiconductor device;

[0028] The source terminal of the first wide bandgap semiconductor device is connected to the drain terminal of the second wide bandgap semiconductor device and one end of the second switching module respectively;

[0029] The drain end of the first wide bandgap semiconductor device serves as the first end of the high-frequency module;

[0030] The source terminal of the second wide bandgap semiconductor device serves as the second terminal of the high-frequency module.

[0031] Optionally, the first switching module includes a first switching switch and a first inductor;

[0032] One end of the first switch is connected to the output port of the low-frequency module;

[0033] The other end of the first switch is connected to one end of the first inductor, and the other end of the first inductor is connected to the power grid through the coupling transformer.

[0034] Optionally, the second switching module includes a second switch and a second inductor;

[0035] One end of the second switch is connected to the output port of the high-frequency module;

[0036] The other end of the second switch is connected to one end of the second inductor, and the other end of the second inductor is connected to the power grid through the coupling transformer.

[0037] Optionally, the filter is a passive filter.

[0038] Optionally, the first switch and the second switch are vacuum circuit breakers.

[0039] A second aspect of the present invention provides a power quality regulation method, applied to the above-mentioned power quality regulation device, comprising:

[0040] Obtaining a low-frequency compensation current and a high-frequency compensation current of the power quality regulation device;

[0041] Determining whether the low-frequency compensation current is less than the high-frequency compensation current;

[0042] When the low-frequency compensation current is less than the high-frequency compensation current, opening the first switch of the power quality adjustment device and closing the second switch of the power quality adjustment device;

[0043] When the low-frequency compensation current is greater than or equal to the high-frequency compensation current, the first switch and the second switch are closed.

[0044] It can be seen from the above technical solutions that the present invention has the following advantages:

[0045] The present application manages the power grid based on the low-frequency module, high-frequency module and neutral point clamping module set in the device. Compared with the traditional power management device, the present application manages the voltage-type power quality such as voltage sag of the power grid through the neutral point clamping module, and can manage the current-type power quality such as reactive power and harmonics of the power grid through the high-frequency module and the low-frequency module. At the same time, the low-frequency module and the high-frequency module are connected to the power grid through the first switching module and the second switching module respectively. According to the required compensation current size, the high-frequency module and the low-frequency module are reasonably switched on and off, which further improves the operating efficiency of the device and thus improves the reliability of the distribution network operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 A schematic structural diagram of a power quality regulation device provided in Embodiment 1 of the present invention;

[0048] Figure 2 A schematic structural diagram of a conventional power quality regulation device provided in the first embodiment of the present invention;

[0049] Figure 3 A modulation principle diagram of the power quality regulation device provided in the first embodiment of the present invention;

[0050] Figure 4 A schematic diagram of the modulation principle of the low-frequency module provided in the first embodiment of the present invention;

[0051] Figure 5 A schematic diagram of the modulation principle of the high-frequency module provided in the first embodiment of the present invention;

[0052] Figure 6 Schematic diagram of output current modulation of the power quality regulation device provided in the first embodiment of the present invention;

[0053] Figure 7 This is a flowchart of the steps of a power quality adjustment method provided in the second embodiment of the present invention. DETAILED DESCRIPTION

[0054] Embodiments of the present invention provide a power quality regulation device and method for resolving the technical problem that, in the prior art, voltage and current problems in a distribution network are comprehensively managed mainly through a unified power quality conditioner. However, due to the voltage resistance, current flow level, and physical limits of semiconductor power devices, it is difficult to further increase the power density of the unified power quality conditioner, thereby reducing the reliability of the distribution network operation.

[0055] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0056] For easier understanding, see Figure 1-6 , an embodiment of the present invention provides a power quality adjustment device, comprising a low-frequency module, a high-frequency module, a neutral point clamping module, a first switching module and a second switching module;

[0057] The output port of the low-frequency module is connected to one end of the first switching module, and the output port of the high-frequency module is connected to one end of the second switching module;

[0058] The other end of the first switching module and the other end of the second switching module are connected to the power grid through a coupling transformer;

[0059] The output port of the neutral point clamping module is connected to the power grid through a filter, and the first end of the neutral point clamping module is connected to the first end of the low frequency module and the first end of the high frequency module respectively;

[0060] The second end of the neutral point clamping module is connected to the second end of the low frequency module and the second end of the high frequency module respectively;

[0061] The third end of the neutral point clamping module is connected to the third end of the low-frequency module.

[0062] In an embodiment of the present invention, a power quality regulation device includes a low-frequency module, a high-frequency module, a neutral point clamping module, a first switching module, and a second switching module. The output port of the low-frequency module is connected in series with one end of the first switching module, and the output port of the high-frequency module is connected in series with one end of the second switching module. The other end of the first switching module and the other end of the second switching module are connected to the power grid via a coupling transformer. The other end of the first switching module and the other end of the second switching module are connected to the power grid via a coupling transformer. The second end of the neutral point clamping module is connected to the second end of the low-frequency module and the second end of the high-frequency module, respectively. The third end of the neutral point clamping module is connected to the third end of the low-frequency module. The output port of the neutral point clamping module is connected to an LC filter and then connected to the power grid via a coupling transformer.

[0063] It is worth mentioning that the power quality control device is provided with a compensation small current mode and a compensation large current mode. When the power quality control device compensates the current i o_ref Less than the maximum compensation current i of the high-frequency module hbmax When the compensation current i o_ref Greater than or equal to the maximum compensation current i of the high-frequency module hbmax When the first switching module is closed, the second switching module is closed. The high-frequency module and the low-frequency module in the power quality control device are both put into operation and jointly output the compensation current i o_ref , to achieve efficient operation of the device.

[0064] See Figure 1As shown, the neutral point clamping module includes a single-phase neutral point clamping unit, a first capacitor C1 and a second capacitor C2; the first end of the single-phase neutral point clamping unit is connected to the positive electrode of the first capacitor C1, and the positive electrode of the first capacitor C1 serves as the first end of the neutral point clamping module; the second end of the single-phase neutral point clamping unit is connected to the negative electrode of the second capacitor C2, and the negative electrode of the second capacitor C2 serves as the second end of the neutral point clamping module; the third end of the single-phase neutral point clamping unit is connected to the negative electrode of the first capacitor C1 and the positive electrode of the second capacitor C2, respectively, and the third end of the single-phase neutral point clamping unit serves as the third end of the neutral point clamping module; the output port of the single-phase neutral point is connected to the power grid through a filter.

[0065] In an embodiment of the present invention, the neutral point clamping module includes a single-phase neutral point clamping unit (single-phase NPC module), a first capacitor C1, and a second capacitor C2. The first end of the single-phase neutral point clamping unit is connected to the positive electrode of the first capacitor C1, and the positive electrode of the first capacitor C1 serves as the first end of the neutral point clamping module and is respectively connected to the first end of the low-frequency module and the first end of the high-frequency module. The second end of the single-phase neutral point clamping unit is connected to the negative electrode of the second capacitor C2, and the negative electrode of the second capacitor C2 serves as the second end of the neutral point clamping module and is respectively connected to the second end of the low-frequency module and the second end of the high-frequency module. The third end of the single-phase neutral point clamping unit is respectively connected to the negative electrode of the first capacitor C1 and the positive electrode of the second capacitor C2 on the common DC bus, and the third end of the single-phase neutral point clamping unit serves as the third end of the neutral point clamping module. The output port of the single-phase neutral point is connected to an LC filter, which is connected to the power grid through a coupling transformer.

[0066] It is worth mentioning that see Figure 3 As shown in FIG, the neutral point clamping module uses pulse width modulation (PWM) to output a three-level pulse voltage, which can achieve the control of grid-side voltage-type power quality problems.

[0067] See Figure 1As shown, the single-phase neutral point clamping unit includes a first IGBT module T1, a second IGBT module T2, a third IGBT module T3, a fourth IGBT module T4, a first diode D1, and a second diode D2; the emitter of the first IGBT module T1 is respectively connected to the collector of the second IGBT module T2 and the cathode of the first diode D1, and the collector of the first IGBT module T1 serves as the first end of the single-phase neutral point clamping unit; the emitter of the second IGBT module T2 is respectively connected to the collector of the third IGBT module T3 and one end of the filter; the anode of the first diode D1 serves as the third end of the single-phase neutral point clamping unit; the emitter of the third IGBT module T3 is respectively connected to the collector of the fourth IGBT module T4 and the anode of the second diode D2, and the emitter of the fourth IGBT module T4 serves as the second end of the single-phase neutral point clamping unit; the anode of the first diode D1 is connected to the cathode of the second diode D2.

[0068] In an embodiment of the present invention, a single-phase neutral point clamping unit includes a first IGBT module T1, a second IGBT module T2, a third IGBT module T3, a fourth IGBT module T4, a first diode D1, and a second diode D2. The first, second, third, and fourth IGBT modules T1, T2, T3, and T4 are all Si IGBT modules. The first, second, third, and fourth IGBT modules T1, T2, T3, and T4 are connected via adjacent collector and emitter nodes. The collector of the first IGBT module T1 serves as the first end of the single-phase neutral point clamping unit, and the emitter of the fourth IGBT module T4 serves as the second end of the single-phase neutral point clamping unit. The anode of the first diode D1 and the cathode of the second diode D2 are respectively connected to the DC bus center point O. The cathode of the first diode D1 is respectively connected to the emitter of the first IGBT module T1 and the collector of the second IGBT module T2. The anode of the second diode D2 is connected to the emitter of the third IGBT module T3 and the collector of the fourth IGBT module T4 respectively. The emitter of the second IGBT module T2 and the collector of the third IGBT module T3 are commonly connected to the output port of the single-phase neutral point clamping unit.

[0069] It is worth mentioning that Si IGBT has the characteristics of strong current capacity and low conduction loss. The single-phase neutral point clamping unit uses 4 Si IGBT modules, which can achieve voltage-type power quality management such as voltage sag.

[0070] See Figure 1As shown, the low-frequency module includes a fifth IGBT module T5, a sixth IGBT module T6, a seventh IGBT module T7, an eighth IGBT module T8, a third diode D3 and a fourth diode D4; the emitter of the fifth IGBT module T5 is respectively connected to the collector of the sixth IGBT module T6 and the cathode of the third diode D3, and the collector of the fifth IGBT module T5 serves as the first end of the low-frequency module; the emitter of the sixth IGBT module T6 is respectively connected to the collector of the seventh IGBT module T7 and one end of the first switching module; the emitter of the seventh IGBT module T7 is respectively connected to the collector of the eighth IGBT module T8 and the anode of the fourth diode D4, and the emitter of the eighth IGBT module T8 serves as the second end of the low-frequency module; the anode of the third diode D3 is connected to the cathode of the fourth diode D4, and the anodes of the three diodes serve as the third end of the low-frequency module.

[0071] In an embodiment of the present invention, the low-frequency module includes a fifth IGBT module T5, a sixth IGBT module T6, a seventh IGBT module T7, an eighth IGBT module T8, a third diode D3, and a fourth diode D4. The fifth, sixth, seventh, and eighth IGBT modules T5, T6, T7, and T8 are all Si IGBT modules. The fifth, sixth, seventh, and eighth IGBT modules T5, T6, T7, and T8 are connected via adjacent collector and emitter nodes. The collector of the fifth IGBT module T5 serves as the first terminal of the low-frequency module, and the emitter of the eighth IGBT module T8 serves as the second terminal of the low-frequency module. The cathode of the third diode D3 is connected to the emitter of the fifth IGBT module T5 and the collector of the sixth IGBT module T6, respectively. The anode of the third diode D3 and the cathode of the fourth diode D4 share a DC bus capacitor with the single-phase neutral point clamping unit. The anode of the fourth diode D4 is connected to the emitter of the seventh IGBT module T7 and the collector of the eighth IGBT module T8 respectively. The emitter of the sixth IGBT module T6 and the collector of the seventh IGBT module T7 are commonly connected to the output port of the low-frequency module.

[0072] It is worth mentioning that the low-frequency module uses the characteristics of the Si IGBT module with strong current capacity and low conduction loss to output a large current containing low-order harmonics i npc , in order to achieve the management of grid electricity.

[0073] See Figure 1 As shown, the high frequency module includes a first wide bandgap semiconductor device T9 and a second wide bandgap semiconductor device T 10 The source terminal of the first wide bandgap semiconductor device T9 is respectively connected to the second wide bandgap semiconductor device T 10The drain end of the first wide bandgap semiconductor device T9 is connected to one end of the second switching module; the drain end of the first wide bandgap semiconductor device T9 serves as the first end of the high frequency module; the second wide bandgap semiconductor device T 10 The source terminal serves as the second terminal of the high frequency module.

[0074] In the embodiment of the present invention, the high frequency module includes a first wide bandgap semiconductor device T9 and a second wide bandgap semiconductor device T 10 , and the first wide bandgap semiconductor device T9 and the second wide bandgap semiconductor device T 10 The first wide bandgap semiconductor device T9 and the second wide bandgap semiconductor device T 10 The drain terminal of the first wide bandgap semiconductor device T9 and the second wide bandgap semiconductor device T are connected through adjacent source and drain nodes. 10 The source terminal of the first wide bandgap semiconductor device T9 is connected to the positive electrode of the first capacitor C1 and the negative electrode of the second capacitor C2 on the common DC bus. 10 The drain terminals are commonly connected to the output port of the high frequency module.

[0075] It is worth mentioning that the high-frequency module uses the characteristics of low switching loss and high operating switching frequency of SiC-based devices to output a small current i containing high-order harmonics. hb .i npc and i hb The combined power quality control device outputs a compensation current i to the grid. o .

[0076] See Figure 1 As shown, the first switching module includes a first switching switch and a first inductor; one end of the first switching switch is connected to the output port of the low-frequency module; the other end of the first switching switch is connected to one end of the first inductor, and the other end of the first inductor is connected to the power grid through a coupling transformer.

[0077] In an embodiment of the present invention, the first switching module includes a first switch and a first inductor. One end of the first switch is connected to the output port of the low-frequency module. The other end of the first switch is connected to a coupling transformer via the first inductor, thereby connecting to the power grid. The first switching module can control the activation and deactivation of the low-frequency module.

[0078] See Figure 1 As shown, the second switching module includes a second switching switch and a second inductor; one end of the second switching switch is connected to the output port of the high-frequency module; the other end of the second switching switch is connected to one end of the second inductor, and the other end of the second inductor is connected to the power grid through a coupling transformer.

[0079] In an embodiment of the present invention, the second switching module includes a second switch and a second inductor. One end of the second switch is connected to the output port of the high-frequency module. The other end of the second switch is connected to a coupling transformer via a second inductor, thereby connecting to the power grid. The second switch can control the activation and deactivation of the high-frequency module.

[0080] It should be noted that the filter is a passive filter.

[0081] In the embodiment of the present invention, the filter is a passive filter. The neutral point clamping module is connected to the power grid using a passive filter, which can not only filter out harmonics of a specific frequency, but also take into account the need for reactive power compensation.

[0082] It should be noted that the first switch and the second switch are vacuum circuit breakers.

[0083] In an embodiment of the present invention, the first switching switch and the second switching switch are vacuum circuit breakers, and the high-frequency module and the low-frequency module are connected to the power grid through the first switching switch and the second switching switch, respectively. Since the vacuum circuit breaker has overload protection, short-circuit protection and undervoltage protection functions, the safety of the line and the power quality regulation device can be ensured.

[0084] It is worth mentioning that see Figure 4 As shown in the figure, the low-frequency module, high-frequency module and neutral point clamp module all achieve current compensation through PWM modulation. Among them, the low-frequency module adopts PWM modulation with a lower carrier frequency to output the large fundamental current portion of the total current. Through the dual closed-loop control of voltage and current, the output compensation current reference value i of the power quality control device can be obtained. o_ref , then the low frequency module outputs the compensation current reference value i npc_ref It can be expressed as:

[0085] inpc_ref=kio_ref

[0086] Among them, k is the proportional coefficient of the high-frequency and low-frequency module compensation currents. Due to the use of low-frequency carrier PWM modulation, the low-frequency module outputs the compensation current i npc There are some low-order harmonic currents. Figure 5 As shown, the high-frequency module uses PWM modulation with a higher carrier frequency to compensate for the small fundamental current while eliminating the output current i of the low-frequency module. npc The low-order harmonic current in the high-frequency module outputs the compensation current reference value i hb_ref It can be expressed as:

[0087] ihb_ref=io_ref-inpc

[0088] It is worth mentioning that see Figure 6As shown in the figure, after the output currents of the high-frequency module and the low-frequency module are superimposed, the output compensation current of the power quality control device only contains i hb_ref It can be seen that the power quality control device fully utilizes the high switching frequency advantage of SiC devices to further improve the control capability of the device.

[0089] In an embodiment of the present invention, the present application manages the power grid based on the low-frequency module, high-frequency module and neutral point clamping module set in the device. Compared with the traditional power management device, the present application manages the voltage-type power quality such as voltage sag of the power grid through the neutral point clamping module, and can manage the current-type power quality such as reactive power and harmonics of the power grid through the high-frequency module and the low-frequency module. At the same time, the low-frequency module and the high-frequency module are connected to the power grid through the first switching module and the second switching module respectively. According to the required compensation current size, the high-frequency module and the low-frequency module are reasonably switched on and off, which further improves the operation efficiency of the device and thus improves the reliability of the distribution network operation.

[0090] See also Figure 7 , Figure 7 This is a flow chart of the steps of a power quality adjustment method provided in the second embodiment of the present invention.

[0091] The present invention provides a power quality regulation method, comprising:

[0092] Step 201: Obtain a low-frequency compensation current and a high-frequency compensation current of a power quality control device;

[0093] Step 202: determine whether the low-frequency compensation current is smaller than the high-frequency compensation current;

[0094] Step 203: When the low-frequency compensation current is less than the high-frequency compensation current, the first switch of the power quality adjustment device is opened and the second switch of the power quality adjustment device is closed;

[0095] Step 204: When the low-frequency compensation current is greater than or equal to the high-frequency compensation current, close the first switch and the second switch.

[0096] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0097] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

[0098] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A power quality control device, characterized in that: It includes a low-frequency module, a high-frequency module, a neutral point clamping module, a first switching module and a second switching module; The output port of the low-frequency module is connected to one end of the first switching module, and the output port of the high-frequency module is connected to one end of the second switching module; The other end of the first switching module and the other end of the second switching module are connected to the power grid through a coupling transformer; The output port of the neutral point clamping module is connected to the power grid through a filter, and the first end of the neutral point clamping module is connected to the first end of the low-frequency module and the first end of the high-frequency module respectively; The second end of the neutral point clamping module is connected to the second end of the low-frequency module and the second end of the high-frequency module respectively; The third end of the neutral point clamping module is connected to the third end of the low-frequency module; The low-frequency module includes a fifth IGBT module, a sixth IGBT module, a seventh IGBT module, an eighth IGBT module, a third diode and a fourth diode; The emitter of the fifth IGBT module is connected to the collector of the sixth IGBT module and the cathode of the third diode respectively, and the collector of the fifth IGBT module serves as the first end of the low-frequency module; The emitter of the sixth IGBT module is connected to the collector of the seventh IGBT module and one end of the first switching module respectively; The emitter of the seventh IGBT module is connected to the collector of the eighth IGBT module and the anode of the fourth diode respectively, and the emitter of the eighth IGBT module serves as the second end of the low-frequency module; The anode of the third diode is connected to the cathode of the fourth diode, and the anodes of the three diodes serve as the third end of the low-frequency module; The high-frequency module includes a first wide-bandgap semiconductor device and a second wide-bandgap semiconductor device; The source terminal of the first wide bandgap semiconductor device is connected to the drain terminal of the second wide bandgap semiconductor device and one end of the second switching module respectively; The drain end of the first wide bandgap semiconductor device serves as the first end of the high-frequency module; The source terminal of the second wide bandgap semiconductor device serves as the second terminal of the high-frequency module.

2. The power quality control device according to claim 1, characterized in that: The neutral point clamping module includes a single-phase neutral point clamping unit, a first capacitor and a second capacitor; The first end of the single-phase neutral point clamping unit is connected to the positive electrode of the first capacitor, and the positive electrode of the first capacitor serves as the first end of the neutral point clamping module; The second end of the single-phase neutral point clamping unit is connected to the negative electrode of the second capacitor, and the negative electrode of the second capacitor serves as the second end of the neutral point clamping module; The third end of the single-phase neutral point clamping unit is connected to the negative electrode of the first capacitor and the positive electrode of the second capacitor respectively, and the third end of the single-phase neutral point clamping unit serves as the third end of the neutral point clamping module; The output port of the single-phase neutral point is connected to the power grid through the filter.

3. The power quality control device according to claim 2, characterized in that: The single-phase neutral point clamping unit includes a first IGBT module, a second IGBT module, a third IGBT module, a fourth IGBT module, a first diode and a second diode; The emitter of the first IGBT module is connected to the collector of the second IGBT module and the cathode of the first diode respectively, and the collector of the first IGBT module serves as the first end of the single-phase neutral point clamping unit; The emitter of the second IGBT module is connected to the collector of the third IGBT module and one end of the filter respectively; The anode of the first diode serves as the third terminal of the single-phase neutral point clamping unit; The emitter of the third IGBT module is connected to the collector of the fourth IGBT module and the anode of the second diode respectively, and the emitter of the fourth IGBT module serves as the second end of the single-phase neutral point clamping unit; The anode of the first diode is connected to the cathode of the second diode.

4. The power quality control device according to claim 1, characterized in that: The first switching module includes a first switching switch and a first inductor; One end of the first switch is connected to the output port of the low-frequency module; The other end of the first switch is connected to one end of the first inductor, and the other end of the first inductor is connected to the power grid through the coupling transformer.

5. The power quality control device according to claim 4, characterized in that: The second switching module includes a second switch and a second inductor; One end of the second switch is connected to the output port of the high-frequency module; The other end of the second switch is connected to one end of the second inductor, and the other end of the second inductor is connected to the power grid through the coupling transformer.

6. The power quality control device according to claim 1, characterized in that: The filter is a passive filter.

7. The power quality control device according to claim 5, characterized in that: The first switch and the second switch are vacuum circuit breakers.

8. A method for regulating power quality, characterized in that: The power quality control device according to any one of claims 1 to 7 comprises: Obtaining a low-frequency compensation current and a high-frequency compensation current of the power quality regulation device; Determining whether the low-frequency compensation current is less than the high-frequency compensation current; When the low-frequency compensation current is less than the high-frequency compensation current, opening the first switch of the power quality adjustment device and closing the second switch of the power quality adjustment device; When the low-frequency compensation current is greater than or equal to the high-frequency compensation current, the first switch and the second switch are closed.

Images