Multi-mode switching dynamic voltage restoration device, control method and power system

Abstract

The application relates to a multi-mode switching type dynamic voltage recovery device, a control method and a power system, which comprises a three-phase dynamic voltage restorer assembly, a switch assembly and a detection control assembly; the switch assembly comprises a power grid bypass switch, a power grid series-in switch, a neutral point series-in switch and a neutral point bypass switch; the detection control assembly is connected with the three-phase dynamic voltage restorer assembly and the switch assembly respectively; the detection control assembly is used for collecting power distribution network electrical parameters; the power grid operation state is determined according to the power distribution network electrical parameters; and the on-off state of the switch assembly and the output parameters of the three-phase dynamic voltage restorer assembly are controlled according to the power grid operation state. Through on-off control of the switch device, the dynamic voltage restorer can adapt to various operation states of the power grid, effectively improves the utilization rate, and reduces the device cost.

Description

Technical Field

[0001] This application relates to the field of power quality management technology for distribution networks, and in particular to a multi-mode switching dynamic voltage recovery device, control method, and power system. Background Technology

[0002] With the deepening of smart grid construction, the distribution network structure is becoming increasingly complex, and the high penetration rate of nonlinear loads and distributed power sources has led to frequent power quality problems, seriously affecting the power supply reliability of the distribution network and the normal operation of electrical equipment. The Dynamic Voltage Restorer (DVR), as a core device for power quality management in distribution networks, can quickly compensate for voltage sags, three-phase asymmetry, and other problems, making it a key device for solving voltage quality issues in distribution networks.

[0003] However, traditional dynamic voltage restorers have a single function, only able to compensate for voltage fluctuations during grid voltage changes. They remain idle during normal grid operation or when ground faults occur, resulting in extremely low equipment utilization and wasted investment, making the cost-effectiveness of the equipment investment low. Meanwhile, active arc suppression devices used in distribution networks to mitigate single-phase ground faults also suffer from long-term idleness due to the limited frequency of single-phase ground faults and short arc suppression duration, further increasing the overall cost of power quality management in distribution networks.

[0004] Existing improvements to dynamic voltage restorers mainly focus on topology optimization, such as modular multilevel topology and transformerless back-to-back topology. Although these have broadened the working range of voltage compensation and increased power density, they have not achieved functional expansion and still cannot solve the core problem of low equipment utilization. Summary of the Invention

[0005] Therefore, it is necessary to provide a multi-mode switching dynamic voltage recovery device, control method, and power system that can effectively improve equipment utilization in response to the above-mentioned technical problems.

[0006] In a first aspect, this application provides a multi-mode switching dynamic voltage recovery device, comprising: a three-phase dynamic voltage recovery unit assembly, a switching assembly, and a detection and control assembly; wherein the detection and control assembly is respectively connected to the three-phase dynamic voltage recovery unit assembly and the switching assembly;

[0007] The switching assembly includes a grid bypass switch, a grid series-connected switch, a neutral point series-connected switch, and a neutral point bypass switch; the grid bypass switch is installed between the three-phase power supply of the distribution network and the three-phase load of the distribution network, the grid series-connected switch is installed between the three-phase dynamic voltage restorer assembly and the output terminal of the three-phase power supply of the distribution network, the neutral point series-connected switch is installed between the three-phase dynamic voltage restorer assembly and the neutral point of the distribution network, and the neutral point bypass switch is installed between the neutral point of the distribution network and the grounding point;

[0008] The detection and control component is used to collect electrical parameters of the power distribution network; determine the operating status of the power grid based on the electrical parameters of the power distribution network; control the on / off state of the switching component and adjust the output parameters of the three-phase dynamic voltage restorer component based on the operating status of the power grid.

[0009] In one embodiment, the three-phase dynamic voltage restorer assembly includes a converter unit, an energy storage unit, and a filter unit; the energy storage unit is connected to the DC side of the converter unit, and the filter unit is connected between the AC side of the converter unit and the power distribution network.

[0010] The converter unit includes a fully controlled bridge converter; the energy storage unit includes an energy storage capacitor; and the filter unit includes a filter inductor.

[0011] In one embodiment, the power grid operating state includes a normal operating state, a single-phase ground fault state, a voltage sag state, and an energy self-recovery state; wherein, the distribution network enters the energy self-recovery state after the fault state of a single-phase ground fault or a voltage sag state ends, and enters the normal operating state after the energy self-recovery state ends.

[0012] The detection and control component includes an acquisition unit, a status determination unit, a switch control unit, and a converter drive unit;

[0013] The acquisition unit is connected to the three-phase power supply of the distribution network, the three-phase load of the distribution network, and the neutral point of the distribution network, respectively. The acquisition unit is used to acquire the electrical parameters of the distribution network and send the electrical parameters of the distribution network to the status determination unit. The electrical parameters of the distribution network include the three-phase power supply side voltage, the neutral point voltage, the three-phase load side voltage, and the load current.

[0014] The status determination unit is used to determine the power grid operating status based on the power distribution network electrical parameters, and generate a corresponding status signal based on the current power grid operating status, and send the status signal to the switch control unit and the converter drive unit respectively.

[0015] The switch control unit is used to control the on / off state of each switch component according to the status signal;

[0016] The converter drive unit is used to control the three-phase dynamic voltage restorer assembly to output target parameters according to the status signal.

[0017] In one embodiment, if the state determination unit determines that the power grid is in normal operating condition, the switch control unit controls the power grid bypass switch and the neutral point bypass switch to close, and controls the power grid series-connected switch and the neutral point series-connected switch to open.

[0018] If the state determination unit determines that the power grid operating state is a voltage sag state; the switch control unit controls the power grid series switch to close and the neutral point bypass switch to close, and controls the power grid bypass switch and the neutral point series switch to open; the converter drive unit controls the three-phase dynamic voltage restorer assembly to output the target voltage;

[0019] If the state determination unit determines that the power grid operating state is a single-phase ground fault state; the switch control unit controls the power grid bypass switch and the neutral point series switch to close, and controls the power grid series switch and the neutral point bypass switch to open; the converter drive unit controls the three-phase dynamic voltage restorer assembly to output the target current;

[0020] If the state determination unit determines that the power grid is in an energy self-recovery state, the switch control unit controls the power grid series switch to close and the neutral point bypass switch to close, and controls the power grid bypass switch and the neutral point series switch to open; the converter drive unit controls the three-phase dynamic voltage restorer assembly to output a reference voltage.

[0021] Secondly, this application also provides a control method for a multi-mode switching dynamic voltage recovery device, employing the multi-mode switching dynamic voltage recovery device as described in the first aspect, the method comprising:

[0022] Collect electrical parameters of the power distribution network;

[0023] The power grid operating status is determined based on the aforementioned power distribution network electrical parameters;

[0024] The on / off state of the control switch assembly is determined according to the power grid operating status, and the output parameters of the three-phase dynamic voltage restorer assembly are adjusted accordingly.

[0025] In one embodiment, the power distribution network electrical parameters include three-phase power supply side voltage and neutral point voltage; determining the power grid operating status based on the power distribution network electrical parameters includes:

[0026] If the offset of the neutral point voltage is greater than or equal to the first preset threshold, the power grid operating state is determined to be a single-phase ground fault state.

[0027] If the voltage offset of the three-phase power supply side is greater than or equal to the second preset threshold, the power grid operating state is determined to be a voltage sag state.

[0028] If the offset of the neutral point voltage is less than the first preset threshold and the voltage of the three-phase power supply side is less than the second preset threshold, the power grid operation status is determined to be a normal operation status.

[0029] In one embodiment,

[0030] The power grid operating states include normal operation state, single-phase ground fault state, voltage sag state, and energy self-recovery state; wherein, the distribution network enters the energy self-recovery state after the fault state of single-phase ground fault or voltage sag state ends, and enters the normal operation state after the energy self-recovery state ends.

[0031] The step of controlling the on / off state of the switching components and adjusting the output parameters of the converter unit according to the power grid operating state includes:

[0032] If the power grid is determined to be in a normal operating state, the power grid bypass switch and the neutral point bypass switch are closed, and the power grid series-connected switch and the neutral point series-connected switch are opened.

[0033] If the power grid operating state is determined to be a voltage sag state, control the power grid series switch to close and the neutral point bypass switch to close, control the power grid bypass switch and the neutral point series switch to open; control the three-phase dynamic voltage restorer assembly to output the target voltage;

[0034] If the power grid is determined to be in a single-phase ground fault state, control the power grid bypass switch and the neutral point series switch to close, and control the power grid series switch and the neutral point bypass switch to open; control the three-phase dynamic voltage restorer assembly to output the target current;

[0035] If the power grid is determined to be in an energy self-recovery state, control the power grid series switch to close and the neutral point bypass switch to close, control the power grid bypass switch and the neutral point series switch to open; control the three-phase dynamic voltage restorer assembly to output a reference voltage.

[0036] In one embodiment, the power distribution network electrical parameters further include system voltage, three-phase load-side voltage, and load current; controlling the converter unit to output the target voltage includes:

[0037] Calculate the voltage drop depth of the power grid based on the reference amplitude of the grid voltage before the voltage drop and the system voltage after the voltage drop.

[0038] The choice between a pure reactive power compensation strategy and a minimum active power compensation strategy is determined based on the voltage drop depth of the power grid.

[0039] The target voltage is calculated based on the pure reactive power compensation strategy or the minimum active power compensation strategy;

[0040] The three-phase dynamic voltage restorer assembly is controlled to output the target voltage to the distribution network.

[0041] In one embodiment, controlling the converter unit to output a target current includes:

[0042] The faulty phase that experienced the ground fault is determined based on the voltage on the three-phase power supply side.

[0043] Calculate the target current corresponding to the fault phase based on Kirchhoff's current law and the fault arc suppression strategy;

[0044] The three-phase dynamic voltage restorer assembly is controlled to inject the target current into the neutral point of the distribution network.

[0045] Thirdly, this application also provides a power system, including a distribution network and the multi-mode switching dynamic voltage recovery device described in the first aspect.

[0046] In summary, this application proposes a multi-mode switching dynamic voltage restoration device, control method, and power system, comprising: a three-phase dynamic voltage restorer assembly, a switching assembly, and a detection and control assembly; the switching assembly includes a grid bypass switch, a grid series switch, a neutral point series switch, and a neutral point bypass switch; the detection and control assembly is connected to both the three-phase dynamic voltage restorer assembly and the switching assembly; the detection and control assembly is used to collect electrical parameters of the distribution network; determine the grid operating state based on the electrical parameters of the distribution network; and control the on / off state of the switching assembly and adjust the output parameters of the three-phase dynamic voltage restorer assembly based on the grid operating state. This application, through the on / off control of the switching devices, enables the dynamic voltage restorer to adapt to various grid operating states, effectively improving utilization while reducing device costs. Attached Figure Description

[0047] Figure 1 This is a block diagram of a multi-mode switching dynamic voltage recovery device in one embodiment;

[0048] Figure 2 This is a circuit topology diagram of a multi-mode switching dynamic voltage recovery device in one embodiment;

[0049] Figure 3 This is a circuit topology diagram of a three-phase dynamic voltage restorer assembly in one embodiment;

[0050] Figure 4This is a circuit topology diagram of a converter unit in one embodiment;

[0051] Figure 5 This is a circuit topology diagram of a multi-mode switching dynamic voltage recovery device in voltage compensation mode in one embodiment;

[0052] Figure 6 This is a circuit topology diagram of a multi-mode switching dynamic voltage recovery device in ground fault mitigation mode in one embodiment;

[0053] Figure 7 This is a block diagram of the detection control component in one embodiment;

[0054] Figure 8 This is a control block diagram for fault arc suppression control under a single-phase ground fault state in one embodiment.

[0055] Figure 9 This is an output voltage vector diagram under a pure reactive power compensation strategy in one embodiment.

[0056] Figure 10 This is an output voltage vector diagram under the minimum active power compensation strategy in one embodiment;

[0057] Figure 11 This is a control block diagram for voltage compensation control during a voltage sag in one embodiment.

[0058] Figure 12 This is an output voltage vector diagram under the energy self-recovery state in one embodiment;

[0059] Figure 13 This is a control block diagram of the energy self-recovery state in one embodiment;

[0060] Figure 14 This is a flowchart illustrating the control method of a multi-mode switching dynamic voltage recovery device in one embodiment.

[0061] Summary of attached image labels:

[0062] Three-phase dynamic voltage restorer assembly-110, switch assembly-120, detection and control assembly-130, acquisition unit-131, status determination unit-132, switch control unit-133, converter drive unit-134. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0064] In one embodiment, such as Figure 1As shown, a multi-mode switching dynamic voltage recovery device is provided, including: a three-phase dynamic voltage restorer assembly 110, a switching assembly 120, and a detection and control assembly 130. The detection and control assembly 130 is connected to both the three-phase dynamic voltage restorer assembly 110 and the switching assembly 120.

[0065] Specifically, the topology diagram of the multi-mode switching dynamic voltage recovery device provided in this embodiment is as follows: Figure 2 As shown. In this embodiment, the AC side of the three-phase dynamic voltage restorer assembly 110 is connected to the distribution network. Specifically, the three-phase dynamic voltage restorer assembly 110 provided in this embodiment includes a first dynamic voltage restorer, a second dynamic voltage restorer, and a third dynamic voltage restorer. The AC side of the first dynamic voltage restorer is connected to phase A or the neutral point of the distribution network, the AC side of the second dynamic voltage restorer is connected to phase B or the neutral point of the distribution network, and the AC side of the third dynamic voltage restorer is connected to phase C or the neutral point of the distribution network.

[0066] In this embodiment, the power distribution network includes equipment and components such as three-phase power supply, three-phase load, ground leakage resistance, ground capacitance, and ground fault transition resistance. Figure 2 As shown, , and For the electromotive force of the power supply in the distribution network, , and Measure voltage for a three-phase power supply. The neutral point voltage, , and This is the voltage on the three-phase load side. , and For the leakage resistance to ground of the distribution network, , and For the distribution network to ground capacitance, This refers to the transition resistance during grounding faults. Three-phase power supplies power three-phase loads, which can be equipment or systems. The actual type of three-phase load can be determined based on the specific application scenario. Ground leakage resistance reflects the insulation condition of equipment or lines. By monitoring changes in ground leakage resistance, insulation faults in equipment or lines can be detected promptly. Ground capacitance is the capacitance formed between the transmission line and the ground. Grounding fault transition resistance is the transient resistance experienced by the short-circuit current flowing through the fault point when a grounding fault occurs in the power system. It should be noted that the structure of the distribution network can be determined based on the actual conditions of the distribution network in the specific application scenario.

[0067] In this embodiment, the switching assembly 120 includes a power grid bypass switch, a power grid series switch, a neutral point series switch, and a neutral point bypass switch. For example... Figure 2 As shown, It is a power grid bypass switch. A switch is connected in series with the power grid. A switch is inserted in series at the neutral point. This is a neutral point bypass switch. Specifically, it is a power grid bypass switch. A switch is installed between the three-phase power supply and the three-phase load of the distribution network, with the power grid connected in series. A switch is connected in series at the neutral point between the three-phase dynamic voltage restorer assembly 110 and the output terminal of the three-phase power supply in the distribution network. A neutral point bypass switch is installed between the three-phase dynamic voltage restorer assembly 110 and the neutral point of the distribution network. It is installed between the neutral point and the grounding point of the distribution network. For example... Figure 2 As shown, the neutral point of the distribution network in this embodiment is point N.

[0068] In this embodiment, different on / off states of the switch assembly 120 correspond to different connection states between the three-phase dynamic voltage restorer assembly 110 and the power distribution network. For example, in the power grid bypass switch... and neutral point bypass switch All switches are closed, while the power grid is connected in series with the switch. and neutral point series switch With all circuits disconnected, the three-phase dynamic voltage restorer assembly 110 is not connected to the distribution network. (This is in the context of the grid bypass switch.) and neutral point series switch All closed, neutral point bypass switch Switches connected in series with the power grid With all circuits disconnected, the AC side of the three-phase dynamic voltage restorer assembly 110 is connected to the neutral point of the distribution network. The neutral point bypass switch... Switches connected in series with the power grid All closed, power grid bypass switch and neutral point series switch When all phases are disconnected, the AC side of the three-phase dynamic voltage restorer assembly 110 is connected to the output terminal of the three-phase power supply of the distribution network.

[0069] In this embodiment, as Figure 2 and Figure 3 As shown, the three-phase dynamic voltage restorer assembly 110 includes a converter unit, an energy storage unit, and a filter unit. Figure 3 As shown, within a single dynamic voltage restorer, the energy storage unit is connected to the DC side of the converter unit, and the filter unit is connected between the AC side of the converter unit and the distribution network.

[0070] like Figure 4 As shown, the converter unit includes a fully controlled bridge converter. In this embodiment, the converter unit of the three-phase dynamic voltage restorer assembly 110 adopts an H-bridge unit structure. The H-bridge unit structure consists of at least four Insulated-Gate Bipolar Transistor (IGBT) power devices. Figure 4 As shown, the converter unit in this embodiment consists of an H-bridge structure composed of four IGBT power devices, namely... , , and In this embodiment, the energy storage unit includes an energy storage capacitor. The filtering unit includes a filtering inductor. Figure 3 As shown, For DVR filter inductor, This refers to energy storage capacitors. It's important to note that the actual structures of the energy storage and filtering units can be adaptively configured according to the needs of the specific application scenario. For example, the energy storage unit can be configured as a supercapacitor and / or a flywheel energy storage device. In practical applications, the filter inductor can effectively filter out harmonics from the converter output, ensuring the waveform quality of electrical quantities injected into the distribution network. The energy storage capacitor provides a stable DC-side voltage to the converter module, effectively improving the response speed of voltage compensation and fault arc suppression.

[0071] In practical applications, the three-phase dynamic voltage restorer assembly 110 mainly outputs corresponding compensation voltage or compensation current by adjusting the power devices of each IGBT in the converter unit. For example... Figure 5 and Figure 6 As shown, , and The voltage injected into the grid for the three-phase DVR, Inject current into the neutral point of the distribution network into the three-phase DVR.

[0072] In this embodiment, the detection and control component 130 is used to collect electrical parameters of the distribution network; determine the operating status of the power grid based on the electrical parameters of the distribution network; control the on / off state of the switch component 120 and adjust the output parameters of the three-phase dynamic voltage restorer component 110 based on the operating status of the power grid.

[0073] Specifically, the multi-mode switching dynamic voltage recovery device provided in this embodiment has at least two fault management modes: a dynamic voltage compensation mode and a ground fault management mode. In actual operation, the distribution network has at least four operating states: normal operation, single-phase ground fault, voltage sag, and energy self-recovery. That is, the power grid operating states in this embodiment include normal operation, single-phase ground fault, voltage sag, and energy self-recovery. The dynamic voltage compensation mode of the multi-mode switching dynamic voltage recovery device corresponds to the voltage sag state of the distribution network, and the ground fault management mode corresponds to the single-phase ground fault state. In practical application, the distribution network is in normal operation when no abnormalities occur. After a single-phase ground fault occurs, it enters the single-phase ground fault state. After a voltage sag occurs, it enters the voltage sag state. After the fault states of single-phase ground fault or voltage sag end, the distribution network enters the energy self-recovery state, and after the energy self-recovery state ends, it enters the normal operation state.

[0074] In this embodiment, the multi-mode switching dynamic voltage recovery device provides switching fault management modes by controlling the on / off states of each switching component 120 to adapt to different real-time conditions of the distribution network. Furthermore, by adjusting the output parameters of the three-phase dynamic voltage restorer component 110 through the detection and control component 130, in conjunction with the mode switching of the switching components 120, effective resolution of multiple types of faults is achieved. It should be noted that the multi-mode switching dynamic voltage recovery device provided in this embodiment can at least be used to manage voltage sags and single-phase grounding faults to ensure the normal operation of the distribution network.

[0075] In summary, this embodiment provides a multi-mode switching dynamic voltage recovery device. Through the integrated structural design of the three-phase dynamic voltage restorer component 110, the switching component 120, and the detection and control component 130, it breaks through the limitation of the traditional single function of DVR. By switching the on and off sequence of the switching component 120, the functions of voltage compensation and fault arc suppression are integrated. The functions that originally required two independent devices are integrated into one device, which greatly improves the utilization rate of DVR equipment and reduces the investment and land cost of power quality management in distribution networks.

[0076] In one embodiment, such as Figure 7 The detection and control component 130 shown includes a data acquisition unit 131, a status determination unit 132, a switch control unit 133, and a converter drive unit 134.

[0077] In this embodiment, the acquisition unit 131 is connected to the three-phase power supply, the three-phase load, and the neutral point of the distribution network. Specifically, the acquisition unit 131 is used to acquire electrical parameters of the distribution network and send these parameters to the status determination unit 132. These electrical parameters include the three-phase power supply voltage, neutral point voltage, three-phase load voltage, and load current. In this embodiment, the acquisition unit 131 can use Hall voltage sensors and / or Hall current sensors to acquire the electrical parameters. It should be noted that this embodiment does not limit the actual structure and circuit composition of the acquisition unit 131; appropriate devices and circuits can be configured according to the needs of the actual application scenario. In this embodiment, the acquisition unit 131 is also equipped with an analog-to-digital conversion circuit to convert the analog signals of the acquired electrical parameters of the distribution network into digital signals. The acquisition unit 131 sends the converted digital signals to the status determination unit 132, so that the status determination unit 132 can determine the operating status of the power grid based on the electrical parameters.

[0078] In this embodiment, the state determination unit 132 is used to determine the power grid operating state based on the electrical parameters of the distribution network, and generate corresponding state signals based on the current power grid operating state, and send the state signals to the switch control unit 133 and the converter drive unit 134 respectively. The state signals correspond to the power grid operating state of the distribution network.

[0079] In one embodiment, the state determination unit 132 is specifically used to determine the grid operation state as a single-phase ground fault state if the offset of the neutral point voltage is greater than or equal to a first preset threshold; to determine the grid operation state as a voltage sag state if the offset of the three-phase power supply side voltage is greater than or equal to a second preset threshold; and to determine the grid operation state as a normal operation state if the offset of the neutral point voltage is less than the first preset threshold and the three-phase power supply side voltage is less than the second preset threshold.

[0080] In this embodiment, the actual values ​​of the first and second preset thresholds can be set according to the needs of the actual application scenario. For example, if the phase voltage amplitude offset on the three-phase power supply side is greater than or equal to 10% of the original amplitude, i.e., the voltage drop depth is greater than or equal to 0.1, the power grid operating state can be determined to be a voltage sag state. If the neutral point-to-ground voltage offset is greater than or equal to 15% of the phase voltage amplitude, the power grid operating state can be determined to be a single-phase ground fault state. If none of the above offsets reach the threshold, the power grid operating state is determined to be a normal operating state.

[0081] In this embodiment, the switch control unit 133 is used to control the on / off state of each switch component 120 according to status signals. Specifically, the status signals include a first status signal, a second status signal, and a third status signal. The first status signal corresponds to the normal mode of the switch component 120, the second status signal corresponds to the fault arc suppression mode of the switch component 120, and the third status signal corresponds to the voltage compensation mode and energy self-recovery mode of the switch component 120. Specifically, the switching timing of the switch control unit 133 in different operating modes is shown in Table 1 below:

[0082] Table 1

[0083]

[0084] Where 0 represents the switch being open and 1 represents the switch being closed.

[0085] The converter drive unit 134 is used to control the converter unit output target parameters of the three-phase dynamic voltage restorer assembly 110 according to the status signal. In this embodiment, the converter drive unit 134 includes an SPWM generator. An SPWM generator is a device for generating sinusoidal pulse width modulation (SPWM) signals. The SPWM generator outputs an SPWM signal to control the converter unit output target parameters.

[0086] Based on the above structure, the detection and control component 130 in this embodiment adopts a modular design, realizing the functional separation and coordination of parameter acquisition, status determination, switch control, and converter drive. Each unit performs its own function, improving the logic and accuracy of the control process, enabling rapid response to changes in the grid operating status and achieving seamless mode switching.

[0087] The following sections will provide a detailed introduction to the principles of various operating modes of the multi-mode switching dynamic voltage recovery device, addressing different types of power grid operation states and switch control.

[0088] In one embodiment, if the state determination unit 132 determines that the power grid is in normal operation, the switch control unit 133 controls the power grid bypass switch. and neutral point bypass switch Close, control the power grid series switch and neutral point series switch disconnect.

[0089] In this embodiment, the dynamic voltage restorer is not connected to the distribution network, and the three-phase power supply is directly connected to the grid bypass switch. When supplying power to the load, the multi-mode switching dynamic voltage recovery device is in standby mode and does not consume reactive power.

[0090] If the status determination unit 132 determines that the power grid operating status is a single-phase ground fault, the switch control unit 133 controls the power grid bypass switch. and neutral point series switch Close, control the neutral point bypass switch Switches connected in series with the power grid Disconnect. The converter drive unit 134 controls the three-phase dynamic voltage restorer assembly 110 to output the target current.

[0091] In this embodiment, after the switch control unit 133 controls the on / off state of each switch, the topology is as follows: Figure 6 As shown. Assuming a single-phase ground fault occurs in phase A, according to Kirchhoff's current law:

[0092]

[0093] in, , These are the three-phase ground admittances, This refers to the fundamental angular frequency of the distribution network. To achieve arc suppression during faults, the voltage of the faulty phase should be... It is zero, that is We can obtain:

[0094]

[0095] In addition, if , then Substituting into the above formula, we can obtain the calculation formula for the fault arc suppression strategy:

[0096]

[0097] According to the formula It is known that the injected current is independent of the grounding transition resistance and can completely compensate for the fault point current. Therefore, the converter drive unit 134 controls the three-phase dynamic voltage restorer assembly 110 to output the target current to the neutral point of the distribution network, which can realize fault arc suppression and solve single-phase grounding faults.

[0098] Specifically, such as Figure 8 As shown, according to the calculation formula of the above fault arc suppression strategy, the fault phase voltage... The neutral point current reference value can be calculated. The three-phase dynamic voltage restorer assembly 110 injects current into the neutral point of the distribution network together from its three-phase DVRs. The reference value for the injected current of each DVR is... Finally, current closed-loop control is adopted, and the drive signal of the converter unit is obtained by modulation through an SPWM generator.

[0099] If the state determination unit 132 determines that the power grid operating state is a voltage sag, the switch control unit 133 controls the power grid bypass switch. and neutral point series switch Disconnect, control the grid connection switch and neutral point bypass switch to close. Converter drive unit 134 controls the three-phase dynamic voltage restorer assembly 110 to output the target voltage.

[0100] In this embodiment, after the switch control unit 133 controls the on / off state of each switch, the topology is as follows: Figure 5 As shown. In this embodiment, a minimum energy compensation strategy is adopted, using the grid voltage before the system voltage drop. As the reference vector, , and These are the system voltage, load voltage, and load current after the voltage drop, respectively. This represents the DVR output voltage. A vector diagram of the pure reactive power compensation strategy is shown below. Figure 9 As shown, the vector diagram of the minimum active power compensation strategy is as follows: Figure 10 As shown. The formula for calculating the voltage sag depth of the power grid is defined as follows:

[0101]

[0102] in, This is the reference amplitude of the grid voltage before the voltage drop.

[0103] exist satisfy At this time, the DVR can achieve pure reactive power compensation. The relationships between the variables are as follows: Figure 9 As shown. Load current. With DVR output voltage Vertical, then under the pure reactive power compensation strategy The amplitude and phase angle can be expressed as:

[0104]

[0105]

[0106] in, The power factor angle is on the load side. At this time, the DVR is in a critical state between pure reactive power compensation and minimum active power compensation, and the DVR bears all reactive power on the load side.

[0107] when At this time, the DVR will operate under minimum energy compensation. To minimize the active power output of the DVR and reduce the capacity of the energy storage capacitor, the DVR output voltage should be adjusted to ensure that the grid voltage and load current are in phase after a voltage drop. In this mode, the DVR operates in minimum active power compensation mode, and the relationships between the variables are as follows: Figure 10 As shown. Then, under the minimum active power compensation strategy... The amplitude and phase angle can be expressed as:

[0108]

[0109]

[0110] Specifically, such as Figure 11 As shown, during the control process, the control is first performed according to the pure reactive power compensation strategy and the minimum active power compensation strategy, respectively. The formulas for calculating the amplitude and phase angle are used to calculate the reference amplitude of the DVR injection voltage under pure reactive power compensation and minimum active power compensation, respectively, based on the grid voltage after the voltage drop, the load-side voltage, and the load-side power factor. and phase angle By combining the two, the injection voltage reference values ​​for the two cases can be obtained respectively. and Then according to and( The magnitude relationship between the two values ​​is used for pattern detection to obtain the final injection voltage reference value. Finally, a voltage closed-loop control method is adopted, and the power device drive signal is obtained through SPWM modulation.

[0111] If the state determination unit 132 determines that the power grid is in an energy self-recovery state, the switch control unit 133 controls the power grid bypass switch. and neutral point series switch Disconnect, control the grid connection switch and neutral point bypass switch to close; converter drive unit 134 controls the three-phase dynamic voltage restorer assembly 110 to output reference voltage.

[0112] In this embodiment, to eliminate the need for an additional charging device and to maximize the advantages of the energy storage DVR, energy self-recovery after fault resolution is essential. During normal grid operation, the DVR output voltage is controlled... , making and Equal amplitude, such as Figure 12 As shown, where, This refers to the DVR output voltage. The phase angle difference between the mains voltage and the DVR output voltage. This represents the phase angle difference between the load-side voltage and the grid voltage. As can be seen, It is closely related to the energy flow between the DVR and the power grid. When At this time, energy flows from the power grid to the DVR, which is in a self-recovering energy state.

[0113] when At other times, the situation is reversed. Therefore, it is possible to maintain Achieve self-recovery of power for the DVR. Definition and They are respectively The active and reactive components. Analyzing the energy flow direction reveals that... The larger the DVR, the more active power it absorbs. The absorbed active power is:

[0114]

[0115] Based on the relationship between the power grid, the DVR output power, and the load-side power, the above equation can be rewritten as:

[0116]

[0117] Let the apparent power of the system be And at this time Then the above formula can be rewritten as:

[0118]

[0119] but, and The phase angle difference is:

[0120]

[0121] Because the active power absorbed by the DVR is Decision, when At this time, the absorbed active power is at its maximum, which is:

[0122]

[0123] At this time, the reference voltage The formulas for calculating the amplitude and phase angle are:

[0124]

[0125]

[0126] like Figure 13 As shown, based on phase angle control, under the condition that the load current and the grid voltage are in phase, i.e. At this time, the DVR absorbs the maximum active power, and the load-side voltage during the energy self-recovery period is reduced. and power factor angle Substitute the reference voltage The reference amplitude of the DVR injection voltage is obtained from the formulas for calculating the amplitude and phase angle. and reference phase angle The two are combined to obtain the injection voltage reference value, i.e., the reference voltage. Finally, voltage closed-loop control is used, and the power device drive signal is obtained through SPWM modulation.

[0127] In summary, this embodiment provides a multi-mode switching dynamic voltage recovery device. The detection and control component 130 determines the grid operating status in real time, controls the switching component 120 to switch to the corresponding on / off sequence according to different statuses, and adjusts the three-phase converter module to enter the corresponding operating mode. Specifically, dedicated control logic is designed for the two core fault scenarios—single-phase grounding faults and voltage sags—for fault arc suppression and voltage compensation modes, respectively. Furthermore, an energy self-recovery mode is designed after the fault is cleared, enabling energy replenishment of the energy storage module without the need for an additional charging device, ensuring energy reserves for subsequent operation of the device.

[0128] The fault arc suppression mode of the multi-mode switching dynamic voltage recovery device adopts a parallel current injection method for three-phase converter modules, combined with current closed-loop control, making the injected current independent of the grounding transition resistance. This enables full compensation of the fault residual current, reducing the fault phase voltage to zero and completely eliminating the impact of single-phase grounding faults. Simultaneously, the dedicated fault arc suppression on / off timing adapts to the topology requirements of fault management, improving arc suppression efficiency. The voltage compensation mode employs a minimum energy compensation strategy, combining dual-mode switching of pure reactive power compensation and minimum active power compensation. While ensuring load-side voltage stability, it minimizes the active power output of the dynamic voltage restorer, reducing the energy consumption of the energy storage module, lowering the capacity configuration requirements of the energy storage module, and further saving hardware costs. At the same time, the dedicated voltage compensation on / off timing enables series connection of the converter module and the distribution network, adapting to the topology requirements of voltage compensation. The energy self-recovery mode reuses the switching timing of voltage compensation, eliminating the need for additional hardware modifications and charging devices. By controlling the output phase angle and amplitude of the converter module, it enables the energy transfer from the distribution network to the energy storage module. After the fault is cleared, the energy of the energy storage module is quickly replenished, ensuring the device's rapid response capability to subsequent grid faults and simplifying the device structure and operation and maintenance process.

[0129] In one embodiment, such as Figure 14 As shown, a control method for a multi-mode switching dynamic voltage recovery device is provided, which is applied to... Figure 1 Taking the detection and control component in the example, the following steps are included:

[0130] S1401, collects electrical parameters of the power distribution network;

[0131] S1402, Determine the power grid operating status based on the electrical parameters of the distribution network;

[0132] S1403 controls the on / off state of the switch assembly and adjusts the output parameters of the three-phase dynamic voltage restorer assembly according to the grid operation status.

[0133] It should be noted that the specific implementation of the control method provided in this embodiment can be referred to the description of the specific working mode of the multi-mode switching dynamic voltage recovery device in the foregoing embodiments, which will not be repeated here.

[0134] In one embodiment, the distribution network electrical parameters include the three-phase power supply side voltage and the neutral point voltage; determining the grid operating status based on the distribution network electrical parameters includes:

[0135] If the offset of the neutral point voltage is greater than or equal to the first preset threshold, the power grid is determined to be in a single-phase ground fault state; if the offset of the three-phase power supply side voltage is greater than or equal to the second preset threshold, the power grid is determined to be in a voltage sag state; if the offset of the neutral point voltage is less than the first preset threshold and the three-phase power supply side voltage is less than the second preset threshold, the power grid is determined to be in a normal operating state.

[0136] In one embodiment, the power grid operating state includes normal operation state, single-phase ground fault state, voltage sag state, and energy self-recovery state; wherein, the distribution network enters the energy self-recovery state after the fault state of single-phase ground fault state or voltage sag state ends, and enters the normal operation state after the energy self-recovery state ends.

[0137] The on / off state of the switching components and the output parameters of the converter unit are controlled according to the grid operating status, including:

[0138] If the grid operation is determined to be in a normal state, control the grid bypass switch and neutral point bypass switch to close, and control the grid series connection switch and neutral point series connection switch to open; if the grid operation is determined to be in a voltage sag state, control the grid series connection switch and neutral point bypass switch to close, and control the grid bypass switch and neutral point series connection switch to open; control the three-phase dynamic voltage restorer assembly to output the target voltage; if the grid operation is determined to be in a single-phase ground fault state, control the grid bypass switch and neutral point series connection switch to close, and control the grid series connection switch and neutral point bypass switch to open; control the three-phase dynamic voltage restorer assembly to output the target current; if the grid operation is determined to be in an energy self-recovery state, control the grid series connection switch and neutral point bypass switch to close, and control the grid bypass switch and neutral point series connection switch to open; control the three-phase dynamic voltage restorer assembly to output the reference voltage.

[0139] In one embodiment, the electrical parameters of the distribution network also include system voltage, three-phase load-side voltage, and load current; controlling the converter unit to output a target voltage includes:

[0140] Based on the reference amplitude of the grid voltage before the voltage drop and the system voltage after the voltage drop, the grid voltage drop depth is calculated; based on the grid voltage drop depth, a pure reactive power compensation strategy or a minimum active power compensation strategy is determined; based on the pure reactive power compensation strategy or the minimum active power compensation strategy, the target voltage is calculated; and the three-phase dynamic voltage restorer components are controlled to output the target voltage to the distribution network.

[0141] In one embodiment, controlling the converter unit to output a target current includes:

[0142] The faulty phase of the ground fault is determined based on the three-phase power supply side voltage; the target current of the corresponding faulty phase is calculated based on Kirchhoff's current law and the fault arc suppression strategy; and the three-phase dynamic voltage restorer components are controlled to inject the target current into the neutral point of the distribution network.

[0143] In one embodiment, a power system is also provided, including the multi-mode switching dynamic voltage recovery device described in the foregoing embodiments.

[0144] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0145] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A multi-mode switching dynamic voltage recovery device, characterized in that, include: A three-phase dynamic voltage restorer assembly, a switching assembly, and a detection and control assembly; wherein the detection and control assembly is connected to both the three-phase dynamic voltage restorer assembly and the switching assembly. The switching assembly includes a grid bypass switch, a grid series-connected switch, a neutral point series-connected switch, and a neutral point bypass switch; the grid bypass switch is installed between the three-phase power supply of the distribution network and the three-phase load of the distribution network, the grid series-connected switch is installed between the three-phase dynamic voltage restorer assembly and the output terminal of the three-phase power supply of the distribution network, the neutral point series-connected switch is installed between the three-phase dynamic voltage restorer assembly and the neutral point of the distribution network, and the neutral point bypass switch is installed between the neutral point of the distribution network and the grounding point; The detection and control component is used to collect electrical parameters of the power distribution network; determine the operating status of the power grid based on the electrical parameters of the power distribution network; control the on / off state of the switching component and adjust the output parameters of the three-phase dynamic voltage restorer component based on the operating status of the power grid.

2. The multi-mode switching dynamic voltage recovery device according to claim 1, characterized in that, The three-phase dynamic voltage restorer assembly includes a converter unit, an energy storage unit, and a filter unit; the energy storage unit is connected to the DC side of the converter unit, and the filter unit is connected between the AC side of the converter unit and the power distribution network. The converter unit includes a fully controlled bridge converter; the energy storage unit includes an energy storage capacitor; and the filter unit includes a filter inductor.

3. The multi-mode switching dynamic voltage recovery device according to claim 1, characterized in that, The power grid operating states include normal operation state, single-phase ground fault state, voltage sag state, and energy self-recovery state; wherein, the distribution network enters the energy self-recovery state after the fault state of single-phase ground fault or voltage sag state ends, and enters the normal operation state after the energy self-recovery state ends. The detection and control component includes an acquisition unit, a status determination unit, a switch control unit, and a converter drive unit; The acquisition unit is connected to the three-phase power supply of the distribution network, the three-phase load of the distribution network, and the neutral point of the distribution network, respectively. The acquisition unit is used to acquire the electrical parameters of the distribution network and send the electrical parameters of the distribution network to the status determination unit. The electrical parameters of the distribution network include the three-phase power supply side voltage, the neutral point voltage, the three-phase load side voltage, and the load current. The status determination unit is used to determine the power grid operating status based on the power distribution network electrical parameters, and generate a corresponding status signal based on the current power grid operating status, and send the status signal to the switch control unit and the converter drive unit respectively. The switch control unit is used to control the on / off state of each switch component according to the status signal; The converter drive unit is used to control the three-phase dynamic voltage restorer assembly to output target parameters according to the status signal.

4. The multi-mode switching dynamic voltage recovery device according to claim 3, characterized in that, If the state determination unit determines that the power grid is in normal operating condition, the switch control unit controls the power grid bypass switch and the neutral point bypass switch to close, and controls the power grid series switch and the neutral point series switch to open. If the state determination unit determines that the power grid operating state is a voltage sag; The switch control unit controls the closing of the grid connection switch and the neutral point bypass switch, and controls the opening of the grid bypass switch and the neutral point connection switch; the converter drive unit controls the three-phase dynamic voltage restorer assembly to output the target voltage; If the state determination unit determines that the power grid operating state is a single-phase ground fault state; the switch control unit controls the power grid bypass switch and the neutral point series switch to close, and controls the power grid series switch and the neutral point bypass switch to open; the converter drive unit controls the three-phase dynamic voltage restorer assembly to output the target current; If the state determination unit determines that the power grid's operating state is an energy self-recovery state; The switch control unit controls the closing of the grid connection switch and the neutral point bypass switch, and controls the opening of the grid bypass switch and the neutral point connection switch; the converter drive unit controls the output reference voltage of the three-phase dynamic voltage restorer assembly.

5. A control method for a multi-mode switching dynamic voltage recovery device, characterized in that, The method using the multi-mode switching dynamic voltage recovery device as described in any one of claims 1-4 includes: Collect electrical parameters of the power distribution network; The power grid operating status is determined based on the aforementioned power distribution network electrical parameters; The on / off state of the control switch assembly is determined according to the power grid operating status, and the output parameters of the three-phase dynamic voltage restorer assembly are adjusted accordingly.

6. The control method according to claim 5, characterized in that, The electrical parameters of the distribution network include the three-phase power supply side voltage and the neutral point voltage; determining the operating status of the power grid based on the electrical parameters of the distribution network includes: If the offset of the neutral point voltage is greater than or equal to the first preset threshold, the power grid operating state is determined to be a single-phase ground fault state. If the voltage offset of the three-phase power supply side is greater than or equal to the second preset threshold, the power grid operating state is determined to be a voltage sag state. If the offset of the neutral point voltage is less than the first preset threshold and the voltage of the three-phase power supply side is less than the second preset threshold, the power grid operation status is determined to be a normal operation status.

7. The control method according to claim 6, characterized in that, The power grid operating states include normal operation state, single-phase ground fault state, voltage sag state, and energy self-recovery state; wherein, the distribution network enters the energy self-recovery state after the fault state of single-phase ground fault or voltage sag state ends, and enters the normal operation state after the energy self-recovery state ends. The step of controlling the on / off state of the switching components and adjusting the output parameters of the converter unit according to the power grid operating state includes: If the power grid is determined to be in a normal operating state, the power grid bypass switch and the neutral point bypass switch are closed, and the power grid series-connected switch and the neutral point series-connected switch are opened. If the power grid operating state is determined to be a voltage sag state, control the power grid series switch to close and the neutral point bypass switch to close, control the power grid bypass switch and the neutral point series switch to open; control the three-phase dynamic voltage restorer assembly to output the target voltage; If the power grid is determined to be in a single-phase ground fault state, control the power grid bypass switch and the neutral point series switch to close, and control the power grid series switch and the neutral point bypass switch to open; control the three-phase dynamic voltage restorer assembly to output the target current; If the power grid is determined to be in an energy self-recovery state, control the power grid series switch to close and the neutral point bypass switch to close, control the power grid bypass switch and the neutral point series switch to open; control the three-phase dynamic voltage restorer assembly to output a reference voltage.

8. The control method according to claim 7, characterized in that, The electrical parameters of the distribution network also include system voltage, three-phase load-side voltage, and load current; controlling the output target voltage of the converter unit includes: Calculate the voltage drop depth of the power grid based on the reference amplitude of the grid voltage before the voltage drop and the system voltage after the voltage drop. The choice between a pure reactive power compensation strategy and a minimum active power compensation strategy is determined based on the voltage drop depth of the power grid. The target voltage is calculated based on the pure reactive power compensation strategy or the minimum active power compensation strategy; The three-phase dynamic voltage restorer assembly is controlled to output the target voltage to the distribution network.

9. The control method according to claim 7, characterized in that, The control of the converter unit to output the target current includes: The faulty phase that experienced the ground fault is determined based on the voltage on the three-phase power supply side. Calculate the target current corresponding to the fault phase based on Kirchhoff's current law and the fault arc suppression strategy; The three-phase dynamic voltage restorer assembly is controlled to inject the target current into the neutral point of the distribution network.

10. An electric power system, characterized in that, Includes a power distribution network and the multi-mode switching dynamic voltage recovery device as described in any one of claims 1-4.

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