Electric energy quality problem comprehensive treatment device and method based on heterogeneous module cooperation

Abstract

The invention discloses an electric energy quality problem comprehensive treatment device and method based on heterogeneous module cooperation. The device comprises an output module, a direct current bus, a first inverter, a second inverter and a third inverter, wherein the first inverter, the second inverter and the third inverter are ANPC type three-phase inverters; in the first inverter, the second inverter and the third inverter, two switching devices at the output end of the third inverter are WBG devices, the other switching devices are Si IGBT devices, the two ends of a three-phase bridge arm are connected to the positive electrode and the negative electrode of a direct-current bus respectively, and the middle points of the three-phase bridge arm are connected to the neutral point of the direct-current bus; the output end of the first inverter is connected to a power grid in parallel; the output ends of the second inverter and the third inverter are connected in series to a power grid after passing through the output module; and the output module is used for LC filtering and performing corresponding phase superposition on the three-phase output voltage of the second inverter and the three-phase output voltage of the third inverter.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion technology, and in particular to a comprehensive power quality management device and method based on heterogeneous module collaboration. Background Technology

[0002] As the power system shifts from being dominated by thermal power generation to being dominated by distributed renewable energy generation, the entire system exhibits the characteristics of "dual highs"—a high proportion of renewable energy and a high proportion of power electronic equipment—leading to increasingly stringent requirements for power quality management. Simultaneously, emerging high-end industries utilize highly sensitive electrical equipment such as high-precision measuring instruments and CNC machine tools, which have extremely high power quality requirements. Even a voltage quality issue lasting only tens of milliseconds can damage automated production lines, causing significant losses for enterprises. Therefore, ensuring high-quality and reliable power supply has become one of the most pressing issues for the distribution network to address.

[0003] UPQC (Unified Power Quality Controller) can simultaneously address reactive power, harmonics, and transient voltage issues, making it an ideal solution for achieving multifunctional power quality management in a single unit. However, traditional UPQCs face a trade-off between cost and efficiency. To build high-power-density and high-efficiency UPQCs, all-SiC MOSFET devices are typically used to reduce losses during high-frequency switching. However, SiC MOSFET devices suffer from higher cost and lower current-carrying capacity, limiting their application in high-power applications. Using lower-cost all-Si IGBT devices, however, results in significant switching losses due to high-frequency operation, reducing converter efficiency. In response, some researchers have proposed the concept of a hybrid system based on partial power transfer, dividing power transfer into two parallel paths to handle the majority and a small portion of power respectively. However, existing hybrid systems are typically applied to single-phase systems. For three-phase grids, each phase requires a separate hybrid system, resulting in complex structure and control, high cost, and limited direct application.

[0004] Therefore, a new technical solution is urgently needed to address the technical challenge of how to achieve efficient and low-cost comprehensive management of power quality issues in three-phase power grids based on improved UPQC. Summary of the Invention

[0005] This invention provides a device and method for comprehensive management of power quality problems based on heterogeneous module collaboration, which solves the technical problem of how to carry out efficient and low-cost comprehensive management of power quality problems in three-phase power grids based on improved UPQC.

[0006] To achieve the above objectives, the present invention provides a comprehensive power quality management device based on heterogeneous module collaboration, including an output module, a DC bus, and a first inverter, a second inverter, and a third inverter, all of which are ANPC type three-phase inverters.

[0007] In the first, second, and third inverters, the two switching devices at the output of the third inverter are WBG devices, and the remaining switching devices are Si IGBT devices. The two ends of the three-phase bridge arms are respectively connected to the positive and negative terminals of the DC bus, and the midpoints are all connected to the neutral point of the DC bus. The output of the first inverter is connected in parallel to the power grid. The outputs of the second and third inverters are connected in series to the power grid after passing through the output module. The output module is used for LC filtering and for superimposing the corresponding phases of the three-phase output voltages of the second and third inverters.

[0008] Preferably, the output module includes three sub-output modules; each sub-output module includes a first filter inductor, a second filter inductor, a first filter capacitor, a second filter capacitor, and a first transformer.

[0009] The output terminals of the three phases of the second and third inverters are connected to the sub-output module in a one-to-one correspondence. Taking one phase as an example, it includes: The output terminals of the second and third inverters are connected to the input terminals of the first and second filter inductors, respectively. The output terminal of the second filter inductor is connected to the positive terminal of the first filter capacitor, and the negative terminal of the first filter capacitor is grounded. The capacitor voltage of the first filter capacitor is connected in series with the first transformer to the output terminal of the first filter inductor, and after being superimposed with the output voltage of the second inverter, it is connected to the positive terminal of the second filter capacitor, and the negative terminal of the second filter capacitor is grounded. The sub-output module uses the capacitor voltage of the second filter capacitor as its output voltage.

[0010] Preferably, it also includes three second transformers and three bypass switches.

[0011] After passing through the output modules at the output terminals of the second and third inverters, the positive terminal of the second filter capacitor in the three corresponding sub-output modules serves as the output terminal of the sub-output module. The output terminals of the three corresponding sub-output modules are connected to the power grid in series through independent second transformers, and a bypass switch is connected in parallel on the secondary side of each second transformer. The bypass switch is used to control whether the sub-output module outputs.

[0012] Preferably, when the power grid needs to perform reactive power compensation, harmonic current compensation, and three-phase imbalance management, the first inverter is used to independently compensate for the negative sequence and zero sequence components in reactive power, harmonic current, and load current.

[0013] When the power grid requires transient voltage management, the second and third inverters work together to perform the first process, and the transient voltage management is achieved based on the first process.

[0014] When the power grid requires steady-state voltage management, the first inverter, the second inverter, and the third inverter work together to perform a second process, which enables steady-state voltage management.

[0015] Preferably, when the power grid requires reactive power compensation, harmonic current compensation, and three-phase imbalance mitigation, it includes: When the power grid requires reactive power compensation and harmonic current compensation, the first inverter is used to detect current harmonics and generate reactive power compensation reference current through the dq detection method, and to achieve reactive power and harmonic current compensation using the triangular wave comparison method.

[0016] When the power grid requires three-phase imbalance management, the first inverter is used to compensate for the negative sequence and zero sequence components in the load current after separating the positive sequence, negative sequence and zero sequence components from the three-phase unbalanced load current.

[0017] Preferably, when the power grid requires transient voltage management, it includes: When the power grid requires transient voltage management, the second and third inverters work together to perform a first process, which includes: After obtaining the output reference voltage of the output module by measuring the grid voltage and comparing it with the rated load voltage, the second and third inverters are used to compensate the load voltage through the output module with the output reference voltage as the target, based on voltage outer loop PIR control and current inner loop PI control.

[0018] Preferably, when the power grid requires steady-state voltage management, it includes: When the power grid requires steady-state voltage regulation, the first inverter, the second inverter, and the third inverter work together to perform a second process, which includes: The first inverter operates as a rectifier, used to absorb active power from the grid to maintain the voltage stability of the DC bus; the DC bus consists of a first capacitor and a second capacitor connected in series.

[0019] After subtracting the actual value of the DC-side voltage from the reference value and inputting it into the PI controller to obtain the active reference current of the first inverter, the first inverter is also used to stabilize the DC-side voltage based on the active reference current combined with dq decoupling control.

[0020] The second and third inverters are also used to compensate the load voltage through the output module with the output reference voltage as the target. This is based on voltage outer loop PIR control and current inner loop PI control.

[0021] Preferably, in the first and second processing, the compensation of the load voltage through the output module based on the voltage outer loop PIR control and the current inner loop PI control includes: The second inverter is used to process a preset wide range of power and outputs a low-frequency square wave voltage; the third inverter is used to process a preset small range of power and outputs a high-frequency pulse-shaped voltage; the output module is used to eliminate low-frequency harmonics in the low-frequency square wave voltage by using the high-frequency pulse-shaped voltage when performing voltage superposition.

[0022] This invention also provides a comprehensive method for addressing power quality issues based on heterogeneous module collaboration. The method, based on the apparatus of this invention, includes: When the power grid needs to perform reactive power compensation, harmonic current compensation, and three-phase imbalance control, the first inverter independently compensates for the negative sequence and zero sequence components in reactive power, harmonic current, and load current.

[0023] When the power grid requires transient voltage management, the second and third inverters work together to perform the first process, and the transient voltage management is achieved based on the first process.

[0024] When the power grid requires steady-state voltage management, the first inverter, the second inverter, and the third inverter work together to perform a second process, and the steady-state voltage management is achieved based on the second process.

[0025] The present invention has the following beneficial effects: This invention relates to a comprehensive power quality management device based on heterogeneous module collaboration. The series side employs a hybrid system design, consisting of a low-frequency, high-capacity Si IGBT module and a high-frequency, low-capacity hybrid module. The two modules form a three-phase ANPC inverter structure with parallel DC-side connections and series AC-side connections, achieving a balance between low cost and high efficiency while ensuring effective voltage quality management. The main unit uses low-cost Si devices to output a low-frequency square wave voltage, reducing device switching losses. The slave unit uses high-performance WBG devices to output a high-frequency pulse-shaped voltage, offsetting harmonic components introduced by the low-frequency operation of the main unit and ensuring overall output voltage waveform quality. The hybrid system has losses similar to a full WBG device system, but significantly reduces device costs, achieving a comprehensive optimization of efficiency and cost. The device based on this invention can achieve efficient and low-cost comprehensive management of three-phase power quality issues.

[0026] The comprehensive power quality management method based on heterogeneous module collaboration of the present invention, and the device based on the present invention, have the same beneficial effects as the device of the present invention.

[0027] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the device structure according to a preferred embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of an ANPC type three-phase inverter according to a preferred embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of the output module structure according to a preferred embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the working mode of the device of the present invention when the power grid needs to perform reactive power compensation, harmonic current compensation and three-phase imbalance management, according to a preferred embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram of the working mode of the device of the present invention when the power grid needs transient voltage management, according to a preferred embodiment of the present invention.

[0033] Figure 6 This is a schematic diagram of the working mode of the device of the present invention when the power grid needs steady-state voltage management, according to a preferred embodiment of the present invention.

[0034] Figure 7 This is a schematic diagram of the conventional full-power processing method of conventional UPQC in a preferred embodiment of the present invention.

[0035] Figure 8 This is a schematic diagram of the hybrid device power processing method of the improved hybrid system topology of the present invention, which is a preferred embodiment of the present invention.

[0036] Figure 9 This is a simplified topology diagram of a single-phase hybrid system with a series-connected topology, which is a preferred embodiment of the present invention.

[0037] Figure 10 This is a schematic diagram of device replacement according to a preferred embodiment of the present invention.

[0038] Figure 11 This is a schematic diagram of the operating principle after device replacement in a preferred embodiment of the present invention.

[0039] In the attached diagram: 100, First inverter; 200, Second inverter; 300, Third inverter; 400, Output module. Detailed Implementation

[0040] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0041] See Figure 1 In a preferred embodiment of the present invention, a comprehensive power quality management device based on heterogeneous module collaboration is provided, including an output module 400, a DC bus, and a first inverter 100, a second inverter 200, and a third inverter 300, all of which are ANPC type three-phase inverters.

[0042] In the first inverter 100, the second inverter 200, and the third inverter 300, the two switching devices at the output of the third inverter 300 are WBG (Wide Band Gap) devices, and the remaining switching devices are Si IGBT devices. The two ends of the three-phase bridge arms are respectively connected to the positive and negative terminals of the DC bus, and the midpoints are all connected to the neutral point of the DC bus. The output of the first inverter 100 is connected to the grid in parallel after being connected to an inductor. The outputs of the second inverter 200 and the third inverter 300 are connected to the grid in series after passing through the output module 400. The output module 400 is used for LC filtering and for superimposing the corresponding phases of the three-phase output voltages of the second inverter 200 and the third inverter 300.

[0043] In a preferred embodiment of the present invention, see [reference needed]. Figure 2 The first inverter 100, the second inverter 200, and the third inverter 300 are all ANPC type three-phase inverters. Figure 2 The ANPC type three-phase inverter in a preferred embodiment of the present invention will be described using an example: it includes three phases, a, b, and c, with each phase having the same device connection method. Taking phase a as an example, Q a1 emitter and Q a2 Drain and Q a5 The collectors are connected. Q a2 Source and Q a3 The drains are connected and an AC output port is brought out. Q a5 emitter and Q a6 The collector is connected to the DC bus neutral point. Q a6 emitter, Q a3 Source and Q a4 The collectors are connected. Q a1 The collector is connected to the positive terminal of the DC bus. Q a4The emitter is connected to the negative terminal of the DC bus. Figure 2 middle, Q x1 , Q x2 , Q x3 , Q x4 , Q x5 and Q x6 These are the corresponding devices in phases a, b, and c, respectively, where x = a, b, c.

[0044] In the preferred embodiment of the ANPC type three-phase inverter of the present invention, the two switching devices at the output terminal of the third inverter 300 are WBG devices, that is, in phases a, b, and c. Q a2 , Q a3 , Q b2 , Q b3 , Q c2 and Q c3 In a preferred embodiment of the invention, the switching devices are preferably SiC MOSFETs, and the remaining switching devices are all Si IGBT devices. In the first inverter 100 and the second inverter 200, all switching devices are Si IGBT devices. In a preferred embodiment of the invention, the second inverter 200 is a low-frequency, high-capacity Si IGBT module, and the third inverter 300 is a high-frequency, low-capacity hybrid module. The two are connected in parallel on the DC side and in series on the AC side.

[0045] In a preferred embodiment of the present invention, see [reference needed]. Figure 1 and Figure 3 The output module 400 includes three sub-output modules 400; each sub-output module 400 includes a first filter inductor, a second filter inductor, a first filter capacitor, a second filter capacitor, and a first transformer. The output terminals of the three phases of the second inverter 200 and the third inverter 300 are connected to the sub-output module 400 in a one-to-one correspondence. Taking one phase as an example, it includes: The output terminals of the second inverter 200 and the third inverter 300 are respectively connected to the first filter inductor. L a1 Second filter inductor L a2 Input terminal; second filter inductor L a2 The output terminal is connected to the first filter capacitor. C aThe positive terminal, the first filter capacitor C a The negative terminal is grounded; the first filter capacitor C a The capacitor voltage passes through the first transformer. T 1. Connected in series with the first filter inductor L a1 The output terminal of the second inverter 200 is superimposed with the output voltage of the second filter capacitor. C A The positive terminal is connected to the second filter capacitor. C A The negative terminal is grounded; the sub-output module 400 uses the second filter capacitor. C A The capacitor voltage is used as the output voltage.

[0046] In a preferred embodiment of the present invention, see [reference needed]. Figure 1 It also includes three secondary transformers and three bypass switches; After the output terminals of the second inverter 200 and the third inverter 300 pass through the output module 400, the positive terminal of the second filter capacitor in the three corresponding sub-output modules 400 serves as the output terminal of the sub-output module 400; the output terminals of the three corresponding sub-output modules 400 are respectively connected to an independent second transformer. T 2 connected in series to the power grid, wherein each second transformer T Both secondary sides of 2 are connected in parallel with bypass switches. P Bypass switch P Used to control whether the sub-output module 400 outputs.

[0047] In a preferred embodiment of the present invention, when the power grid needs to perform reactive power compensation, harmonic current compensation and three-phase imbalance management, the first inverter 100 is used to independently compensate the negative sequence and zero sequence components in reactive power, harmonic current and load current. When the power grid requires transient voltage management, the second inverter 200 and the third inverter 300 work together to perform the first process, and the transient voltage management is achieved based on the first process. When the power grid requires steady-state voltage management, the first inverter 100, the second inverter 200 and the third inverter 300 work together to perform a second process, and achieve steady-state voltage management based on the second process.

[0048] In a preferred embodiment of the present invention, see [reference needed]. Figure 4 When the power grid needs reactive power compensation, harmonic current compensation, and three-phase imbalance mitigation, it includes: When the power grid requires reactive power compensation and harmonic current compensation, the first inverter 100 is used to detect current harmonics and generate reactive power compensation reference current through the dq detection method, and to achieve reactive power and harmonic current compensation by using the triangular wave comparison method.

[0049] When the power grid requires three-phase imbalance management, the first inverter 100 is used to compensate for the negative sequence and zero sequence components in the load current after separating the positive sequence, negative sequence and zero sequence components from the three-phase unbalanced load current.

[0050] In a preferred embodiment of the present invention, see [reference needed]. Figure 5 When the power grid requires transient voltage management, it includes: When the power grid requires transient voltage management, the second inverter 200 and the third inverter 300 cooperate to perform a first process, which includes: After obtaining the output reference voltage of the output module 400 by measuring the grid voltage and comparing it with the rated load voltage, the second inverter 200 and the third inverter 300 are used to compensate the load voltage through the output module 400 with the output reference voltage as the target, based on voltage outer loop PIR control and current inner loop PI control.

[0051] In a preferred embodiment of the present invention, see [reference needed]. Figure 6 When the power grid requires steady-state voltage management, it includes: When the power grid requires steady-state voltage regulation, the first inverter 100, the second inverter 200, and the third inverter 300 cooperate to perform a second process, which includes: The first inverter 100 operates as a rectifier, used to draw active power from the grid to maintain voltage stability on the DC bus; see also Figure 1 The DC bus consists of a first capacitor connected in series. C 1 and second capacitors C It consists of 2 components.

[0052] After subtracting the actual value of the DC-side voltage from the reference value and inputting it into the PI controller to obtain the active reference current of the first inverter 100, the first inverter 100 is also used to stabilize the DC-side voltage based on the active reference current combined with dq decoupling control.

[0053] The second inverter 200 and the third inverter 300 are also used to compensate the load voltage through the output module 400 with the output reference voltage as the target, based on voltage outer loop PIR control and current inner loop PI control.

[0054] In a preferred embodiment of the present invention, the compensation of the load voltage through the output module 400 based on the voltage outer loop PIR control and the current inner loop PI control in the first and second processes includes: The second inverter 200 is used to process a preset wide range of power and output a low-frequency square wave voltage; the third inverter 300 is used to process a preset small range of power and output a high-frequency pulse-shaped voltage; the output module 400 is used to eliminate low-frequency harmonics in the low-frequency square wave voltage by using the high-frequency pulse-shaped voltage when performing voltage superposition.

[0055] In a preferred embodiment of the present invention, since the second inverter 200 operates at low frequency, its output voltage contains significant low-frequency harmonics. The third inverter 300 operates at high frequency and is responsible for canceling the low-frequency harmonics generated by the second inverter 200, thereby improving the output voltage waveform quality.

[0056] In a preferred embodiment of the present invention, the second inverter 200 uses Si IGBTs to reduce device costs and operates at low frequencies to reduce device switching losses. The third inverter 300 is constructed using a hybrid of Si IGBTs and WBG devices, wherein the Si IGBTs operate at low frequencies and the WBG devices operate at high frequencies to improve device operating efficiency and transmit a small portion of power to reduce device costs.

[0057] This invention relates to a comprehensive power quality management device based on heterogeneous module collaboration. The series side employs a hybrid system design, consisting of a low-frequency, high-capacity Si IGBT module and a high-frequency, low-capacity hybrid module. The two modules form a three-phase ANPC inverter structure with parallel DC-side connections and series AC-side connections, achieving a balance between low cost and high efficiency while ensuring effective voltage quality management. The main unit uses low-cost Si devices to output a low-frequency square wave voltage, reducing device switching losses. The slave unit uses high-performance WBG devices to output a high-frequency pulse-shaped voltage, offsetting harmonic components introduced by the low-frequency operation of the main unit and ensuring overall output voltage waveform quality. The hybrid system has losses similar to a full WBG device system, but significantly reduces device costs, achieving a comprehensive optimization of efficiency and cost.

[0058] In a preferred embodiment of the present invention, a comprehensive method for addressing power quality issues based on heterogeneous module collaboration is also provided. Based on the apparatus of the present invention, the method includes: When the power grid needs to perform reactive power compensation, harmonic current compensation and three-phase imbalance control, the first inverter 100 independently compensates the negative sequence and zero sequence components in reactive power, harmonic current and load current. When the power grid needs transient voltage management, the second inverter 200 and the third inverter 300 cooperate to perform the first process, and the transient voltage management is achieved based on the first process; When the power grid requires steady-state voltage management, the first inverter 100, the second inverter 200 and the third inverter 300 cooperate to perform a second process, and the steady-state voltage management is achieved based on the second process.

[0059] The comprehensive power quality management method based on heterogeneous module collaboration of the present invention, and the device based on the present invention, have the same beneficial effects as the device of the present invention.

[0060] Explanation of principles: See Figure 7 Traditional UPQC (Upgraded Quantization) uses a conventional full-power processing method, requiring high-frequency operation to ensure output voltage waveform quality. Using Si (Silicon Integrated Circuit) devices leads to high system losses, while using WBG (Wastewater Integrated Circuit) devices reduces losses but significantly increases device cost. (See also...) Figure 8 The improved hybrid system topology of this invention employs a series-side converter based on partial power processing and hybrid devices to achieve a trade-off between efficiency and cost in addressing voltage sags, voltage swells, and steady-state voltage issues. The second inverter 200 operates as the master unit, and the third inverter 300 operates as the slave unit. The master unit uses low-cost Si devices to output a low-frequency square wave voltage, reducing device switching losses, but also introducing significant harmonic components. The slave unit uses WBG devices with excellent switching performance to output a high-frequency pulse-shaped voltage, offsetting the harmonic components introduced by the low-frequency operation of the master unit and ensuring the overall output voltage waveform quality. The hybrid system losses are similar to those of a full WBG device system, but the device cost is significantly reduced, achieving a comprehensive optimization of efficiency and cost. Figure 7 and Figure 8 In P in and P o These represent the input power and the output power, respectively.

[0061] Figure 9 To simplify the topology of the improved hybrid system topology of this invention, the master and slave units are connected in parallel on the DC side and in series on the AC side, sharing a common DC voltage. The master unit uses Si IGBT devices to reduce switching losses at power frequency, while the slave unit uses both Si IGBTs and WBG devices to ensure output voltage quality at high frequencies. Simultaneously, the slave unit output employs a turns ratio of... The transformer is connected in series to the output terminal of the master unit. The relationship between the total output voltage and the output voltage of the master and slave units includes: ; in, Indicates the total output voltage; Indicates the main unit output voltage; This indicates the output voltage from the unit.

[0062] The master unit operates at power frequency to handle most of the power, but this introduces significant voltage harmonics. The slave unit operates at high frequency to compensate for these harmonics. Due to the limited current-carrying capacity of WBG devices, the slave unit only handles a portion of the power. Simultaneously, the slave unit output is connected to the master unit output via a transformer with a turns ratio of nT, thereby reducing the current flowing through the slave unit and increasing the system's maximum transmission capacity.

[0063] In a preferred embodiment of the present invention, if the third inverter 300 uses all WBG devices, it will result in a large device cost. Therefore, the present invention only uses the two switching devices at the output terminal of the third inverter 300. Q 2 and Q 3 was replaced with a WBG device. Q 1. Q 4. Q 5 and Q 6. Si IGBT devices are retained to further reduce device costs. In the third inverter 300, the WBG devices operate at high frequency, while the SiIGBTs operate at power frequency to compensate for the low-frequency voltage harmonics in the second inverter 200. For specific device replacement details, please refer to [link to relevant documentation]. Figure 10 .

[0064] In the structure after device replacement, only Q 2. Q 3. Performs high-frequency switching action. Q 1. Q 4. Q 5. Q Unit 6 continues to operate at the power frequency, and its switch status is shown in Table 1. During operation, Q 1. Q 6 and Q 4. Q 5. They always share the same switching signal, and the two pairs of Si devices are in a complementary conduction relationship, SiC MOSFET. Q 2. Q 3 form another pair of complementary switching devices, and their operating principle is as follows: Figure 11 As shown.

[0065] Table 1. Switching modes of ANPC topology after device optimization configuration ; According to the switching mode analysis in Table 1, the ANPC has a total of 4 switching modes after the device is optimized.

[0066] Mode 1: Q 1. Q 2. Q 6 conduction, Q 3. Q 4. Q 5. Turn off, connect capacitor from unit output. C 1. High-order terminal, output voltage isv d / 2.

[0067] Mode 2: Q 1. Q 3. Q 6 conduction, Q 2. Q 4. Q 5. When the circuit is turned off, the output voltage is zero when connected to the neutral point of the capacitor.

[0068] Mode 3: Q 3. Q 4. Q 5 conduction, Q 1. Q 2. Q 6. Turn off, connect capacitor from unit output. C 2. Low-order terminal, output voltage value - v d / 2.

[0069] Mode 4: Q 2. Q 4. Q 5 conduction, Q 1. Q 3. Q When 6 is turned off, the output voltage is zero when connected to the neutral point of the capacitor.

[0070] The output voltages of Mode 2 and Mode 4 are both zero, corresponding to the zero-level phases of the positive and negative half-cycles, respectively.

[0071] From the above analysis, it can be seen that, Q 1. Q 4. Q 5. Q All 6 operate at low frequencies, and the switching state does not change within half a cycle. Si IGBTs can be used to reduce device costs, while optimizing the conduction loss of devices in high-power scenarios. Q 2. Q 3. To handle the high-frequency operation process within half a cycle, WBG devices are used to reduce device switching losses, thereby achieving comprehensive optimization of unit efficiency and cost.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A comprehensive power quality management device based on heterogeneous module collaboration, characterized in that, It includes output modules, DC buses, and first, second, and third inverters, all of which are ANPC type three-phase inverters; In the first inverter, the second inverter, and the third inverter, the two switching devices at the output terminal of the third inverter are WBG devices, and the remaining switching devices are Si IGBT devices. The two ends of the three-phase bridge arms are respectively connected to the positive and negative terminals of the DC bus, and the midpoints are all connected to the neutral point of the DC bus. The output terminal of the first inverter is connected to the power grid in parallel. The output terminals of the second inverter and the third inverter are connected to the power grid in series after passing through the output module. The output module is used for LC filtering and for superimposing the corresponding phases of the three-phase output voltages of the second inverter and the third inverter.

2. The comprehensive power quality management device based on heterogeneous module collaboration according to claim 1, characterized in that, The output module includes three sub-output modules; each sub-output module includes a first filter inductor, a second filter inductor, a first filter capacitor, a second filter capacitor, and a first transformer. The output terminals of the three phases of the second inverter and the third inverter are connected to the sub-output module in a one-to-one correspondence. Taking one phase as an example, it includes: The output terminals of the second inverter and the third inverter are respectively connected to the input terminals of the first filter inductor and the second filter inductor; the output terminal of the second filter inductor is connected to the positive terminal of the first filter capacitor, and the negative terminal of the first filter capacitor is grounded; the capacitor voltage of the first filter capacitor is connected in series with the first transformer to the output terminal of the first filter inductor, and after being superimposed with the output voltage of the second inverter, it is connected to the positive terminal of the second filter capacitor, and the negative terminal of the second filter capacitor is grounded; the sub-output module uses the capacitor voltage of the second filter capacitor as the output voltage.

3. The comprehensive power quality management device based on heterogeneous module collaboration according to claim 2, characterized in that, It also includes three secondary transformers and three bypass switches; After passing through the output module at the output terminals of the second and third inverters, the positive terminal of the second filter capacitor in the three corresponding sub-output modules serves as the output terminal of the sub-output module. The output terminals of the three corresponding sub-output modules are connected to the power grid in series through independent second transformers, wherein a bypass switch is connected in parallel on the secondary side of each second transformer. The bypass switch is used to control whether the sub-output module outputs.

4. The comprehensive power quality management device based on heterogeneous module collaboration according to claim 3, characterized in that, When the power grid needs to perform reactive power compensation, harmonic current compensation and three-phase imbalance control, the first inverter is used to independently compensate the negative sequence and zero sequence components in reactive power, harmonic current and load current. When the power grid requires transient voltage management, the second inverter and the third inverter work together to perform a first process, and achieve transient voltage management based on the first process. When the power grid requires steady-state voltage management, the first inverter, the second inverter, and the third inverter work together to perform a second process, and achieve steady-state voltage management based on the second process.

5. The comprehensive power quality management device based on heterogeneous module collaboration according to claim 3, characterized in that, When the power grid needs reactive power compensation, harmonic current compensation, and three-phase imbalance mitigation, it includes: When the power grid requires reactive power compensation and harmonic current compensation, the first inverter is used to detect current harmonics and generate reactive power compensation reference current through the dq detection method, and to achieve reactive power and harmonic current compensation by using the triangular wave comparison method. When the power grid requires three-phase imbalance management, the first inverter is used to compensate for the negative sequence and zero sequence components in the load current after separating the positive sequence, negative sequence and zero sequence components from the three-phase unbalanced load current.

6. The comprehensive power quality management device based on heterogeneous module collaboration according to claim 5, characterized in that, The requirement for transient voltage management in the power grid includes: When the power grid requires transient voltage management, the second inverter and the third inverter cooperate to perform a first process, which includes: After obtaining the output reference voltage of the output module by measuring the grid voltage and comparing it with the rated load voltage, the second inverter and the third inverter are used to compensate the load voltage through the output module with the output reference voltage as the target, based on voltage outer loop PIR control and current inner loop PI control.

7. The comprehensive power quality management device based on heterogeneous module collaboration according to claim 6, characterized in that, The requirement for steady-state voltage management in the power grid includes: When the power grid requires steady-state voltage regulation, the first inverter, the second inverter, and the third inverter cooperate to perform a second process, which includes: The first inverter operates as a rectifier to absorb active power from the grid to maintain the voltage stability of the DC bus; the DC bus consists of a first capacitor and a second capacitor connected in series. After subtracting the actual value of the DC-side voltage from the reference value and inputting it into the PI controller to obtain the active reference current of the first inverter, the first inverter is also used to perform stable control of the DC-side voltage based on the active reference current combined with dq decoupling control. The second and third inverters are also used to compensate the load voltage through the output module with the output reference voltage as the target, based on voltage outer loop PIR control and current inner loop PI control.

8. The comprehensive power quality management device based on heterogeneous module collaboration according to claim 7, characterized in that, In the first and second processes, the compensation of the load voltage through the output module based on the voltage outer loop PIR control and the current inner loop PI control includes: The second inverter is used to process a preset wide range of power and output a low-frequency square wave voltage; the third inverter is used to process a preset small range of power and output a high-frequency pulse-shaped voltage; the output module is used to eliminate low-frequency harmonics in the low-frequency square wave voltage by means of the high-frequency pulse-shaped voltage when voltage superposition is performed.

9. A comprehensive method for addressing power quality issues based on heterogeneous module collaboration, using the apparatus described in any one of claims 4 to 8, the method comprising: When the power grid needs to perform reactive power compensation, harmonic current compensation and three-phase imbalance control, the first inverter independently compensates the negative sequence and zero sequence components in reactive power, harmonic current and load current. When the power grid needs transient voltage management, the second inverter and the third inverter cooperate to perform a first process, and transient voltage management is achieved based on the first process; When the power grid requires steady-state voltage management, the first inverter, the second inverter, and the third inverter work together to perform a second process, and steady-state voltage management is achieved based on the second process.

Images