Voltage regulation method, power conversion module and power quality control system

Abstract

The invention provides a voltage regulation method, a power conversion module and an electric energy quality control system, and belongs to the technical field of power electronics. The method comprises the following steps: acquiring the network side voltage of a load in real time, and sending the network side voltage of the load and a preset target voltage threshold to an off-grid inverter; according to the network side voltage of the load and a preset target voltage threshold value, determining a target voltage regulating variable corresponding to each phase voltage in the network side voltage of the load and an absolute value of each target voltage regulating variable; determining the phase synchronization direction of each phase voltage according to the target voltage regulating variable corresponding to each phase voltage; and according to the phase synchronization direction of each phase voltage, the absolute value of each target voltage regulation variable and a preset regulation step length of the off-grid inverter, sequentially regulating the amplitude of each phase voltage, so that the output voltage of the off-grid inverter reaches a preset value. According to the invention, the realization difficulty of voltage regulation of the power quality management system can be reduced, and the reliability of the power quality management system can be improved.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a voltage regulation method, a power conversion module, and a power quality control system. Background Art

[0002] In the field of power quality management, common power quality management equipment includes: shunt compensators or filters, series compensators or filters, etc. Among them, the shunt compensator mainly compensates for harmonics and reactive currents on the load side. In specific scenarios, it can also manage three-phase active power imbalance, realize three-phase energy transfer, and ensure that the three-phase load is approximately balanced; the series compensator mainly compensates for voltage, including fundamental voltage and harmonic voltage. However, the above two types of compensators or filters each have their own advantages and disadvantages. Therefore, the combination of the two compensators has become a universal power quality controller (Unified Power Quality Controller, referred to as UPQC), such as the currently common series-parallel active power compensator or filter. This universal power quality controller can compensate for both current and voltage and has rich functions.

[0003] In the related art, the UPQC system structure is usually composed of two-stage power converters connected back to back. One end of the power converter is connected to the power grid, and the other end is connected in series to the power grid through a transformer, so that a DC bus is formed inside the UPQC system. Among them, the power converter is directly connected to the power grid to form a parallel current compensator, and the power converter is connected in series to the power grid via a transformer to form a series voltage compensator. The DC bus in the UPQC system is controlled by the parallel current compensator, which can not only achieve current compensation but also maintain the stability of the DC bus through active current. In addition, the power converter not only needs to provide occupied capacity for the three-phase current, but also needs to provide energy for the inverter of the subsequent circuit bus, so that the level of the power converter needs to be greater than the power level of the inverter in the subsequent circuit.

[0004] However, when implementing power quality management based on related technologies, the shunt current compensator must compensate for grid current and stabilize the DC bus voltage to provide stable support for subsequent circuits. It cannot address three-phase active power imbalance, resulting in complex functions and high implementation difficulty. Furthermore, varying power levels lead to complex and widely varying power converter algorithms, hindering the modular design and batch management of UPQC systems, leading to reduced reliability. Summary of the Invention

[0005] The purpose of this application is to provide a voltage regulation method, a power conversion module and a power quality control system, which can reduce the difficulty of implementing voltage regulation in the power quality management system and improve the reliability of the power quality management system.

[0006] The embodiment of the present application is implemented as follows:

[0007] According to a first aspect of an embodiment of the present application, a voltage regulation method is provided. The voltage regulation method is applied to an off-grid inverter in a power quality control system. The voltage regulation method includes:

[0008] Obtain the grid-side voltage of the load in real time;

[0009] Determine the target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load and the absolute value of each target voltage adjustment amount according to the grid-side voltage of the load and a preset target voltage threshold;

[0010] Determine the phase synchronization direction of each phase voltage according to the target voltage adjustment amount corresponding to each phase voltage, and the phase synchronization direction includes: in-phase and anti-phase;

[0011] According to the phase synchronization direction of each phase voltage, the absolute value of each target voltage adjustment amount and the preset adjustment step of the off-grid inverter, the amplitude of each phase voltage is adjusted in sequence so that the output voltage of the power quality control system reaches the preset value.

[0012] As a possible implementation, determining a target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load according to the grid-side voltage of the load and a preset target voltage threshold includes:

[0013] Determine the compensation voltage corresponding to each phase voltage based on the difference between each phase voltage in the grid-side voltage of the load and a preset target voltage threshold;

[0014] The target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load is determined according to the compensation voltage corresponding to each phase voltage.

[0015] As a possible implementation method, the phase synchronization direction of each phase voltage is determined according to the target voltage adjustment amount corresponding to each phase voltage, including:

[0016] Determine the adjustment direction of each target voltage adjustment amount according to the target voltage adjustment amount corresponding to each phase voltage, and the adjustment direction includes: forward and reverse;

[0017] The phase synchronization direction of each phase voltage is determined according to the adjustment direction of each target voltage adjustment amount.

[0018] As a possible implementation method, according to the target voltage adjustment amount corresponding to each phase voltage, the adjustment direction of each target voltage adjustment amount is determined, including:

[0019] Determine the value of each target voltage adjustment amount according to the target voltage adjustment amount corresponding to each phase voltage;

[0020] If the value of the target voltage adjustment amount is a positive number, the adjustment direction of the target voltage adjustment amount is positive;

[0021] If the value of the target voltage adjustment amount is a negative number, the adjustment direction of the target voltage adjustment amount is reverse.

[0022] As a possible implementation method, the phase synchronization direction of each phase voltage is determined according to the adjustment direction of each target voltage adjustment amount, including:

[0023] If the adjustment direction of the target voltage adjustment amount is forward, the phase synchronization direction corresponding to the target voltage adjustment amount is in phase;

[0024] If the adjustment direction of the target voltage adjustment amount is reverse, the phase synchronization direction corresponding to the target voltage adjustment amount is anti-phase.

[0025] As a possible implementation method, the amplitude of each phase voltage is adjusted in sequence according to the phase synchronization direction of each phase voltage, the absolute value of each target voltage adjustment amount, and the preset adjustment step size of the off-grid inverter, including:

[0026] Determine whether to perform voltage compensation on each phase voltage according to the absolute value of each target voltage adjustment amount;

[0027] If so, the adjustment range of each phase voltage is determined according to the phase synchronization direction of each phase voltage, and the amplitude of each phase voltage is adjusted in sequence according to the adjustment range of each phase voltage and the preset adjustment step of the off-grid inverter.

[0028] As a possible implementation method, according to the phase synchronization direction of each phase voltage, the adjustment range of each phase voltage is determined, and according to the adjustment range of each phase voltage and the preset adjustment step size of the off-grid inverter, the amplitude of each phase voltage is adjusted in sequence, including:

[0029] If the phase synchronization directions of the voltages of each phase are all in phase, the amplitudes of the voltages of each phase are adjusted in sequence according to the preset adjustment step of the off-grid inverter;

[0030] If at least one of the phase synchronization directions of the phase voltages is in reverse phase, the amplitude of the phase voltages is adjusted in sequence according to the preset adjustment step of the off-grid inverter. After waiting for a preset time, the phase is flipped, and then the amplitude of the phase voltage is adjusted in sequence according to the preset adjustment step of the off-grid inverter.

[0031] As a possible implementation, the power quality control system further includes: a first power conversion unit, a second power conversion unit, and a detection and monitoring module; the first power conversion unit and the second power conversion unit are connected to a three-phase power grid, the output end of the first power conversion unit is respectively connected to the input end of the second power conversion unit and the off-grid inverter, and the detection and monitoring module is respectively connected to the first power conversion unit, the second power conversion unit, and the off-grid inverter in communication. The above method further includes:

[0032] The first power conversion unit provides direct current to the second power conversion unit and the off-grid inverter under the control of the detection and monitoring module;

[0033] The second power conversion unit adjusts the output power of the three-phase power grid under the control of the detection and monitoring module.

[0034] According to a second aspect of an embodiment of the present application, a power conversion module is provided, which is used to implement the steps of the voltage regulation method described in the first aspect.

[0035] A third aspect of the embodiments of the present application provides a power quality control system, the power quality control system comprising: a transformer module, a switch module, a detection and monitoring module, and the power conversion module described in the second aspect above, the power conversion module comprising: a first power conversion unit, a second power conversion unit, and an off-grid inverter;

[0036] One end of the transformer module is connected to the three-phase grid, and the other end of the transformer module is connected to the AC port of the off-grid inverter in the power conversion module;

[0037] The AC port of the first power conversion unit and the AC port of the second power conversion unit are both connected to the three-phase grid, and the DC port of the first power conversion unit is connected to the off-grid inverter and the DC port of the second power conversion unit respectively;

[0038] The AC port of the off-grid inverter is also connected to the switch module, and the detection and monitoring module is respectively communicated with the transformer module and the power conversion module.

[0039] The beneficial effects of the embodiments of the present application include:

[0040] The embodiment of the present application provides a voltage regulation method, which collects the grid-side voltage of the load in real time, and determines the target voltage regulation amount and the absolute value of the target voltage regulation amount corresponding to each phase voltage in the grid-side voltage of the load according to the grid-side voltage of the load and the preset target voltage threshold; determines the phase synchronization direction of each phase voltage in the grid-side voltage of the load according to the voltage regulation value indicated by the target voltage regulation amount corresponding to each phase voltage in the grid-side voltage of the load; and sequentially adjusts each phase voltage in the grid-side voltage of the load according to the phase synchronization direction of each phase voltage in the grid-side voltage of the load, the absolute value of the target voltage regulation amount corresponding to each phase voltage, and the preset regulation step size of the off-grid inverter, so that each phase voltage output by the power quality control system reaches the preset value. In this way, the difficulty of implementing voltage regulation of the power quality management system can be reduced, and the reliability of the power quality management system can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 A schematic diagram of the structure of an off-grid inverter internal voltage regulation compensation provided by an embodiment of the present application;

[0043] Figure 2 A flowchart of a first voltage regulation method provided in an embodiment of the present application;

[0044] Figure 3 A flow chart of a second voltage regulation method provided in an embodiment of the present application;

[0045] Figure 4 A flowchart of a third voltage regulation method provided in an embodiment of the present application;

[0046] Figure 5 A flowchart of a fourth voltage regulation method provided in an embodiment of the present application;

[0047] Figure 6 A flowchart of a fifth voltage regulation method provided in an embodiment of the present application;

[0048] Figure 7 A flowchart of a sixth voltage regulation method provided in an embodiment of the present application;

[0049] Figure 8 A flowchart of a seventh voltage regulation method provided in an embodiment of the present application;

[0050] Figure 9 A voltage variation curve diagram of cross-region voltage regulation of an off-grid inverter provided in an embodiment of the present application;

[0051] Figure 10 A flowchart of an eighth voltage regulation method provided in an embodiment of the present application;

[0052] Figure 11 A schematic diagram of the structure of a power quality control system provided in an embodiment of the present application;

[0053] Figure 12 A control timing diagram of a switch module provided in an embodiment of the present application.

[0054] Description of the drawings: 10: Power quality control system; 101: Transformer module; 102: Switch module; 103: Detection and monitoring module; 104: Power conversion module; 1041: First power conversion unit; 1042: Second power conversion unit; 1043: Off-grid inverter. DETAILED DESCRIPTION

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0056] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0057] In the description of this application, it should be noted that the terms "first", "second", "third", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance. It should also be noted that, unless otherwise clearly specified and limited, the terms "set", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0058] Currently, power quality control systems are implemented using back-to-back two-stage power converters. One end of the power converter is directly connected to the grid, and the power quality control system implements parallel current compensation through this end of the power converter. The other end of the power converter is connected to the grid via a transformer, and the power quality control system implements series voltage compensation through this end of the power converter. However, in this solution, the power quality control system must maintain the stability of the DC bus within the power converter while managing power through the power converter. The power converter not only provides capacity for the three-phase grid but also serves as the downstream inverter. This results in an increased power level and complex functions for the power converter, and it is unable to address active current imbalance. In addition, the different power levels of the various electronic components in the power quality control system lead to increased algorithm differences, resulting in a decrease in the overall coordination of the power quality control system and poor reliability.

[0059] To this end, an embodiment of the present application provides a voltage regulation method that monitors the grid-side voltage of the load in real time and, based on the grid-side voltage of the load and a preset target voltage threshold, sends a three-phase compensation voltage to the AC side of the transformer module in real time. The transformer module adjusts the voltage output from the three-phase grid to the load in real time based on the received three-phase compensation voltage. This simplifies the algorithm function of the off-grid inverter and coordinates the power levels of various electronic components in the power quality control system. This reduces the difficulty of implementing voltage regulation in the power quality management system and improves the reliability of the power quality management system.

[0060] Figure 1 This is a schematic diagram of the structure of an off-grid inverter internal voltage regulation compensation provided by this application, see Figure 1 The voltage regulation method for the off-grid inverter provided in the embodiment of the present application is specifically implemented by a voltage regulation outer loop and a control loop. The voltage regulation outer loop can be set in the power quality control system or in the off-grid inverter. This application takes the voltage regulation outer loop as an example of being set in the off-grid inverter, but it does not mean that the voltage regulation outer loop must be set in the off-grid inverter. This application does not make specific limitations on this.

[0061] It is worth noting that UA_rms* is used to indicate the target voltage threshold corresponding to the preset A-phase grid-side voltage, UA_rms is used to indicate the real-time A-phase grid-side voltage at the load end, |Ua_rms*| is used to indicate the effective value or absolute value of the target voltage regulation amount corresponding to the A-phase grid-side voltage; Ua_rms is used to indicate the compensation voltage corresponding to the A-phase grid-side voltage output from the output end of the off-grid inverter to the transformer; Ia_rms* is used to indicate the preset A-phase AC current given amount, IA_rms is used to indicate the AC current compensation value corresponding to the A-phase AC current actually received at the load input end, Min acts as a comparator, calculates the phase adjustment direction corresponding to each phase grid-side voltage through the sin function and the multiplier, and calculates the instantaneous given amount through the instantaneous value voltage loop and the instantaneous current loop, and outputs the corresponding PWM wave based on the follow-up given amount, and outputs the corresponding three-phase compensation voltage based on the pulse width modulation signal.

[0062] The voltage regulation method provided in the embodiments of the present application is explained in detail below with reference to the accompanying drawings.

[0063] Figure 2 This is a flow chart of a voltage regulation method provided by this application, which is applied to an off-grid inverter in a power quality control system. Figure 2 , an embodiment of the present application provides a voltage regulation method, comprising:

[0064] S201. Obtain the grid-side voltage of the load in real time.

[0065] Optionally, the off-grid inverter samples the load's grid-side voltage in real time through a voltage regulation outer loop, or a detection and monitoring device monitors the load's grid-side voltage in real time and transmits it to the off-grid inverter in real time. The load's grid-side voltage indicates the three-phase grid voltage before the three-phase grid input transformer.

[0066] S202 : Determine a target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load and an absolute value of each target voltage adjustment amount according to the grid-side voltage of the load and a preset target voltage threshold.

[0067] Optionally, the preset target voltage threshold is a rated value corresponding to each phase voltage of the three-phase power grid set in advance by the user, and the user stores the preset target voltage threshold in advance in the off-grid inverter or the power quality control system. If the user stores the preset target voltage threshold in advance in the power quality control system, the power quality control system transmits the preset target voltage threshold to the off-grid inverter via wireless communication technology.

[0068] Optionally, the off-grid inverter calculates the target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load based on the grid-side voltage of the load and a preset target voltage threshold. The target voltage adjustment amount is used to indicate the voltage adjustment span corresponding to each phase voltage in the grid-side voltage of the load, that is, the grid-side voltage of the load combined with the target voltage adjustment amount can reach the preset target voltage threshold.

[0069] Optionally, the absolute value of the target voltage regulation amount is used to indicate a voltage regulation amplitude corresponding to each phase voltage in the grid-side voltage of the load.

[0070] S203 : Determine a phase synchronization direction of each phase voltage according to a target voltage adjustment amount corresponding to each phase voltage, where the phase synchronization direction includes: in-phase and anti-phase.

[0071] Optionally, the phase synchronization direction is used to indicate the voltage regulation direction corresponding to each phase voltage in the grid-side voltage of the load, and the same phase is used to indicate that the voltage regulation direction of the grid-side voltage of the load is the same as the current direction of the grid-side voltage of the load, that is, the phase direction of the grid-side voltage of the load remains unchanged; the opposite phase is used to indicate that the voltage regulation direction of the grid-side voltage of the load is opposite to the current direction of the grid-side voltage of the load, that is, the phase direction of the grid-side voltage of the load changes.

[0072] S204, adjusting the amplitude of each phase voltage in sequence according to the phase synchronization direction of each phase voltage, the absolute value of each target voltage adjustment amount, and the preset adjustment step of the off-grid inverter, so that the output voltage of the power quality control system reaches the preset value.

[0073] Optionally, the preset adjustment step size is set based on the factory specifications of the off-grid inverter. The preset adjustment step size of the off-grid inverter is used to indicate the voltage compensation amplitude that can be completed in a single time when the off-grid inverter performs voltage compensation on each phase voltage. The preset adjustment step size can be 5V, 10V, 15V, etc., and this application does not make specific limitations on this.

[0074] Optionally, when the voltage adjustment value indicated by the target adjustment amount exceeds the preset adjustment step of the off-grid inverter, the off-grid inverter can compensate for the voltage corresponding to the target adjustment amount multiple times. For example, the target adjustment amount corresponding to the A-phase voltage is 15V, the phase adjustment direction of the A-phase voltage is in phase, and the preset adjustment step of the off-grid inverter is 10V. Then, the off-grid inverter outputs a voltage compensation value of 10V for the A-phase voltage for the first time, and outputs a voltage compensation value of 5V for the A-phase voltage for the second time, so that the A-phase voltage reaches the preset target voltage threshold.

[0075] Optionally, the preset value is a voltage value provided by the three-phase power grid to the load end set in advance by the user. The preset value may be 200V, 220V, 240V, etc., and this application does not make any specific limitation on this.

[0076] Optionally, the off-grid inverter outputs voltage compensation values ​​corresponding to each phase voltage in sequence according to the phase adjustment direction of each phase voltage in the grid-side voltage of the load, the voltage adjustment amount corresponding to each phase voltage, and the adjustment step of the off-grid inverter itself, so that the voltage value of each phase voltage output by the power quality control system to the load end reaches a preset value.

[0077] In an embodiment of the present application, the grid-side voltage of the load is collected in real time, and the target voltage adjustment amount and the absolute value of the target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load are determined based on the grid-side voltage of the load and a preset target voltage threshold; the phase synchronization direction of each phase voltage in the grid-side voltage of the load is determined based on the voltage adjustment value indicated by the target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load; and the phase synchronization direction of each phase voltage in the grid-side voltage of the load, the absolute value of the target voltage adjustment amount corresponding to each phase voltage, and the preset adjustment step size of the off-grid inverter are sequentially adjusted so that each phase voltage output by the power quality control system reaches the preset value. In this way, the difficulty of implementing voltage regulation of the power quality management system can be reduced, and the reliability of the power quality management system can be improved.

[0078] In one possible implementation, see Figure 3 The operation of step S202 may specifically be:

[0079] S301 : Determine a compensation voltage corresponding to each phase voltage according to a difference between each phase voltage in the grid-side voltage of the load and a preset target voltage threshold.

[0080] Optionally, the off-grid inverter calculates the difference between each phase voltage in the grid-side voltage of the load and a preset target voltage threshold, and uses the difference between each phase voltage and the preset target voltage threshold as the compensation voltage corresponding to each phase voltage. The compensation voltage is used to indicate the voltage to be adjusted for each phase voltage in the grid-side voltage of the load.

[0081] For example, the phase A voltage in the grid-side voltage of the load is 200V, the phase B voltage is 220V, and the phase C voltage is 240V, and the preset target voltage threshold is 220V. Then, the compensation voltage corresponding to the phase A voltage in the grid-side voltage of the load is 220V-200V=20V, the compensation voltage corresponding to the phase B voltage in the grid-side voltage of the load is 220V-220V=0V, and the compensation voltage corresponding to the phase C voltage in the grid-side voltage of the load is 220V-240V=-20V.

[0082] S302 : Determine a target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load according to the compensation voltage corresponding to each phase voltage.

[0083] Optionally, the off-grid inverter uses the compensation voltage corresponding to each phase voltage as the target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load, and the voltage adjustment value included in the target voltage adjustment amount is the value corresponding to the compensation voltage.

[0084] In one possible implementation, see Figure 4 The operation of step S203 may specifically be:

[0085] S401 : Determine an adjustment direction of each target voltage adjustment amount according to a target voltage adjustment amount corresponding to each phase voltage, where the adjustment direction includes forward and reverse.

[0086] Optionally, the adjustment direction of each target voltage adjustment amount is determined based on the target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load. The adjustment direction is used to indicate whether the voltage compensation of each phase voltage is increasing in the positive direction or decreasing in the negative direction. The same direction is used to indicate that the voltage adjustment direction is increasing in the positive direction, and the reverse direction is used to indicate that the voltage adjustment direction is decreasing in the negative direction.

[0087] For example, if the target voltage adjustment amount corresponding to the A-phase voltage in the grid-side voltage of the load is 20V, the adjustment direction of the target voltage adjustment amount of the A-phase voltage is forward; if the target voltage adjustment amount corresponding to the B-phase voltage in the grid-side voltage of the load is 0V, the adjustment direction of the target voltage adjustment amount of the B-phase voltage is forward; if the target voltage adjustment amount corresponding to the C-phase voltage in the grid-side voltage of the load is -20V, the adjustment direction of the target voltage adjustment amount of the C-phase voltage is reverse.

[0088] S402: Determine the phase synchronization direction of each phase voltage according to the adjustment direction of each target voltage adjustment amount.

[0089] Optionally, according to the adjustment direction of each target voltage adjustment amount, it is determined whether phase reversal is required during the voltage adjustment process of each phase voltage in the grid-side voltage of the load.

[0090] In one possible implementation, see Figure 5 The operation of step S401 may specifically be:

[0091] S501 : Determine the value of each target voltage adjustment amount according to the target voltage adjustment amount corresponding to each phase voltage.

[0092] Optionally, the voltage adjustment value indicated by the target voltage adjustment amount corresponding to each phase voltage is used as the numerical value of each target voltage adjustment amount.

[0093] S502: If the value of the target voltage adjustment amount is a positive number, the adjustment direction of the target voltage adjustment amount is positive.

[0094] Optionally, if the voltage adjustment value included in the target voltage adjustment amount is a positive number, the voltage adjustment direction corresponding to the target voltage adjustment amount is positive, and the positive direction is used to indicate that the off-grid inverter does not need phase flipping when performing voltage compensation.

[0095] S503: If the value of the target voltage adjustment amount is a negative number, the adjustment direction of the target voltage adjustment amount is reverse.

[0096] Optionally, if the voltage adjustment value included in the target voltage adjustment amount is a negative number, the voltage adjustment direction corresponding to the target voltage adjustment amount is reverse, and the reverse direction is used to indicate that the off-grid inverter needs to perform phase reversal when performing voltage compensation.

[0097] In one possible implementation, see Figure 6 The operation of step S402 may specifically be:

[0098] S601: If the adjustment direction of the target voltage adjustment amount is forward, the phase synchronization direction corresponding to the target voltage adjustment amount is in-phase.

[0099] Optionally, when the adjustment direction of the target voltage adjustment amount is positive increase, the phase synchronization direction corresponding to the target voltage adjustment amount is in phase.

[0100] S602: If the adjustment direction of the target voltage adjustment amount is reverse, the phase synchronization direction corresponding to the target voltage adjustment amount is anti-phase.

[0101] Optionally, when the adjustment direction of the target voltage adjustment amount is reverse decrease, the phase synchronization direction corresponding to the target voltage adjustment amount is anti-phase.

[0102] In one possible implementation, see Figure 7 The operation of step S204 may specifically be:

[0103] S701: Determine whether to perform voltage compensation on each phase voltage according to the absolute value of each target voltage adjustment amount.

[0104] Optionally, whether voltage compensation needs to be performed on each phase voltage of the grid-side voltage of the load is determined according to the absolute value of the target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load.

[0105] S702: If yes, determine the adjustment range of each phase voltage according to the phase synchronization direction of each phase voltage, and adjust the amplitude of each phase voltage in sequence according to the adjustment range of each phase voltage and the preset adjustment step of the off-grid inverter.

[0106] Optionally, if it is determined that each phase voltage in the grid-side voltage of the load needs voltage compensation, the off-grid inverter determines the adjustment range of each phase voltage according to the phase synchronization direction corresponding to each phase voltage in the grid-side voltage of the load, and the adjustment range is used to indicate the change range of the voltage regulation process of each phase voltage.

[0107] Optionally, the off-grid inverter adjusts the voltage amplitude of each phase voltage in sequence according to the adjustment range of each phase voltage in the grid-side voltage of the load and the preset adjustment step of the off-grid inverter, so that the voltage amplitude of each phase voltage in the grid-side voltage of the load reaches a preset value.

[0108] In one possible implementation, see Figure 8 The operation of step S702 may specifically be:

[0109] S801: If the phase synchronization directions of the phase voltages are all in phase, the amplitudes of the phase voltages are adjusted in sequence according to the preset adjustment step of the off-grid inverter.

[0110] Optionally, when the phase synchronization directions of the phase voltages are all in phase, the voltage regulation process of the voltage does not require phase reversal, and the off-grid inverter directly adjusts the voltage amplitude of the voltage according to the preset regulation step of the off-grid inverter.

[0111] S802. If at least one phase synchronization direction of the phase voltages is in reverse phase, the amplitude of each phase voltage is adjusted in sequence according to the preset adjustment step of the off-grid inverter. After waiting for a preset time, the phase is flipped, and then the amplitude of each phase voltage is adjusted in sequence according to the preset adjustment step of the off-grid inverter.

[0112] Optionally, when at least one phase synchronization direction of the phase synchronization directions of each phase voltage is in reverse, that is, the adjustment process of the voltage with reverse phase synchronization direction requires phase reversal, the off-grid inverter first reduces the voltage amplitude of the voltage to 0V according to the preset adjustment step, and after waiting for a preset time, determines that the voltage is stable at 0V and the phase is reversed, and the off-grid inverter continues to adjust the voltage amplitude of the voltage according to the preset adjustment step.

[0113] Optionally, the preset time length is a time length set in advance by the user to determine the voltage regulation stability. The preset time length may be 3ms, 5ms, etc., and this application does not make any specific limitation on this.

[0114] As an optional implementation, Figure 9 For a voltage variation curve diagram of cross-region voltage regulation of an off-grid inverter provided in this application, see Figure 9, Ua_rms1* is used to represent the preset target voltage threshold, Ua_rms2* is used to represent the absolute value of the target voltage adjustment amount, and -Ua_rms2* is used to represent the voltage adjustment value when the phase synchronization direction is reverse and the voltage adjustment interval is cross-region, that is, the actual voltage value of the target voltage adjustment amount.

[0115] As an optional embodiment, the power quality control system further includes: a first power conversion unit, a second power conversion unit, and a detection and monitoring module; the first power conversion unit and the second power conversion unit are connected to the three-phase power grid, the output end of the first power conversion unit is connected to the input end of the second power conversion unit and the off-grid inverter respectively, and the detection and monitoring module is communicated with the first power conversion unit, the second power conversion unit, and the off-grid inverter respectively. Figure 10 , the voltage regulation method provided in the embodiment of the present application further includes:

[0116] S1001. Under the control of the detection and monitoring module, the first power conversion unit provides direct current to the second power conversion unit and the off-grid inverter.

[0117] Optionally, the detection and monitoring module can monitor the actual operating status of the first power conversion unit, the second power conversion unit and the off-grid inverter in real time, and send control instructions to the first power conversion unit based on the actual monitoring results of the first power conversion unit. Under the control of the detection and monitoring module, the first power conversion unit provides a DC signal to the second power conversion unit and the off-grid inverter.

[0118] Optionally, the second power conversion unit and the off-grid inverter operate stably under the DC signal provided by the first power conversion unit, which can improve the stability of the power quality control system.

[0119] Optionally, the first power conversion unit may be implemented by an AC-DC converter, or may be implemented by an inverter or a power converter, which is not specifically limited in this application.

[0120] S1002. The second power conversion unit adjusts the output power of the three-phase power grid under the control of the detection and monitoring module.

[0121] Optionally, the detection and monitoring module sends a control instruction to the second power conversion unit based on the actual monitoring result of the second power conversion unit, so that the second power conversion unit outputs a current compensation value to the three-phase power grid to balance the output power of the three-phase power grid.

[0122] The following describes the power conversion module, power quality control system, etc. used to implement the voltage regulation method provided in this application. The specific implementation process and technical effects are described above and will not be repeated below.

[0123] An embodiment of the present application provides a power conversion module, which is used to implement the steps of the above-mentioned voltage regulation method.

[0124] Figure 11 This is a schematic diagram of the structure of a power quality control system provided by this application, see Figure 11 The power quality control system 10 provided in the embodiment of the present application includes: a transformer module 101, a switch module 102, a detection and monitoring module 103 and the above-mentioned power conversion module 104, wherein the power conversion module 104 includes: a first power conversion unit 1041, a second power conversion unit 1042 and an off-grid inverter 1043.

[0125] One end of the transformer module 101 is connected to the three-phase power grid, and the other end of the transformer module 101 is connected to the AC port of the off-grid inverter 1043 in the power conversion module 104 .

[0126] Optionally, one end of the transformer module 101 is used to access the output signals of each phase of the three-phase power grid, and the other end of the transformer module 101 is connected to the AC port of the off-grid inverter 1043. The off-grid inverter 1043 outputs a three-phase compensation voltage to the transformer module 101 via the AC port. The transformer module 101 adjusts the grid-side voltage of each phase load output from the three-phase power grid to the load based on the received three-phase compensation voltage and the transformation ratio.

[0127] The AC port of the first power conversion unit 1041 and the AC port of the second power conversion unit 1042 are both connected to the three-phase grid, and the DC port of the first power conversion unit 1041 is connected to the off-grid inverter 1043 and the DC port of the second power conversion unit 1042 respectively.

[0128] Optionally, the AC port of the first power conversion unit 1041 is connected to the three-phase grid, and the first power conversion unit 1041 obtains the AC signal output by the three-phase grid to the load via the AC port. The DC port of the first power conversion unit 1041 is used to provide a DC signal to the second power conversion unit 1042 and the off-grid inverter 1043.

[0129] Optionally, an AC port of the second power conversion unit 1042 is connected to the three-phase grid, and the second power conversion unit 1042 outputs the current compensation value to the three-phase grid via the AC port.

[0130] The AC port of the off-grid inverter 1043 is also connected to the switch module 102 , and the detection and monitoring module 103 is communicatively connected to the transformer module 101 and the power conversion module 104 , respectively.

[0131] Optionally, the AC port of the off-grid inverter 1043 is also connected to the switch module 102, and the switch module 102 serves as a bypass of the transformer module 101. The switch module 102 can further disconnect the path between the off-grid inverter 1043 and the transformer module 101 when the off-grid inverter 1043 is not running, so as to improve the reliability of the power quality control system 10.

[0132] Optionally, the detection and monitoring module 103 is respectively communicated with the transformer module 101 and the power conversion module 104. The detection and monitoring module 103 can monitor the power conversion on the DC side and the AC side of the transformer module 101 in real time. The detection and monitoring module 103 can also monitor the working status of the first power conversion unit 1041, the second power conversion unit 1042 and the off-grid inverter 1043 in the power conversion module 104 in real time.

[0133] As an optional embodiment, the switch module 102 in the power quality control system 10 provided in the embodiment of the present application is implemented by a plurality of electronic switches and a plurality of mechanical switches, wherein the input end of each electronic switch and the input end of each mechanical switch are connected to the AC port of the off-grid inverter, the output end of each electronic switch and the output end of each mechanical switch are connected to the neutral line of the off-grid inverter, the control end of each electronic switch is connected to the signal control end of the off-grid inverter, and the control end of each mechanical switch is used to connect to an external drive circuit, see Figure 12The control timing of a switch module provided in an embodiment of the present application is specifically as follows: (1) The time period 0-t0 can be regarded as the off-grid inverter being in a non-operating state, the target voltage set value is set to a default value of 0V, the target current set value is set to a default value of 0A, and all electronic switches and mechanical switches are closed; (2) The time period t0-t3 can be regarded as the off-grid inverter being in a startup process. The off-grid inverter receives a startup operation instruction at time t0, disconnects each mechanical switch in the switch module, and the off-grid inverter controls each electronic switch to remain in a non-operating state. In the closed state under the state, the off-grid inverter is short-circuited and started based on the preset target current given value and target voltage given value (the preset target current given value is the sum of the default value 0 plus the current error value and the preset target voltage given value is the sum of the default value 0 plus the voltage error value). A delay period (t0-t1) is added to ensure that the off-grid inverter starts normally. The off-grid inverter outputs 0.1 times the rated current with a small impact on the electronic switch. The off-grid inverter sends a disconnect control instruction to each electronic switch at time t1, and the off-grid inverter controls each electronic switch. The switch is disconnected, and the output voltage of the off-grid inverter is clamped to near 0V. After a delay of a period of time (t1-t2), it is determined that the off-grid inverter has the conditions for normal startup, and at time t2, the target current setting is set to the rated current, and based on the voltage regulation instruction, the target voltage setting is set to the voltage value indicated by the voltage regulation instruction. The off-grid inverter sends a three-phase compensation voltage to the transformer module according to the set target voltage setting and target current setting, that is, the off-grid inverter operates normally; (4) t3-t6 can be regarded as the off-grid inverter's stop operation process. In the process, the off-grid inverter receives the stop operation instruction at time t3. During the period t3-t4, the off-grid inverter first sets the target current setting to a smaller value greater than 0, such as 0.1 times the rated current, and sets the target voltage setting to a default value near 0V, and waits for the period t4-t5. At time t5, the off-grid inverter first controls the closing of each electronic switch, delays to ensure the normal and reliable execution of the electronic switch, and detects whether the voltage of the electronic switch is normal. If the electronic switch is operating normally, the off-grid inverter closes each mechanical switch at time t6, and the off-grid inverter stops operating normally.

[0134] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited to them. Any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

[0135] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A voltage regulation method, characterized in that: An off-grid inverter applied to a power quality control system, the voltage regulation method comprises: Obtain the grid-side voltage of the load in real time; Determine, according to the grid-side voltage of the load and a preset target voltage threshold, a target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load and an absolute value of each target voltage adjustment amount; Determine the phase synchronization direction of each phase voltage according to the target voltage adjustment amount corresponding to each phase voltage, wherein the phase synchronization direction includes: in-phase and anti-phase; According to the phase synchronization direction of each phase voltage, the absolute value of each target voltage adjustment amount and the preset adjustment step of the off-grid inverter, the amplitude of each phase voltage is adjusted in sequence so that the output voltage of the power quality control system reaches the preset value.

2. The voltage regulation method according to claim 1, characterized in that: The determining, according to the grid-side voltage of the load and a preset target voltage threshold, a target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load comprises: Determining a compensation voltage corresponding to each phase voltage according to a difference between each phase voltage in the grid-side voltage of the load and a preset target voltage threshold; According to the compensation voltage corresponding to each phase voltage, a target voltage adjustment amount corresponding to each phase voltage in the grid-side voltage of the load is determined.

3. The voltage regulation method according to claim 1, characterized in that: The step of determining the phase synchronization direction of each phase voltage according to the target voltage adjustment amount corresponding to each phase voltage includes: Determine the adjustment direction of each target voltage adjustment amount according to the target voltage adjustment amount corresponding to each phase voltage, wherein the adjustment direction includes: forward and reverse; According to the adjustment direction of each target voltage adjustment amount, the phase synchronization direction of each phase voltage is determined.

4. The voltage regulation method according to claim 3, characterized in that: The step of determining the adjustment direction of each target voltage adjustment amount according to the target voltage adjustment amount corresponding to each phase voltage includes: Determine the value of each target voltage adjustment amount according to the target voltage adjustment amount corresponding to each phase voltage; If the value of the target voltage adjustment amount is a positive number, the adjustment direction of the target voltage adjustment amount is positive; If the value of the target voltage adjustment amount is a negative number, the adjustment direction of the target voltage adjustment amount is reverse.

5. The voltage regulation method according to claim 3, characterized in that: The step of determining the phase synchronization direction of each phase voltage according to the adjustment direction of each target voltage adjustment amount includes: If the adjustment direction of the target voltage adjustment amount is forward, the phase synchronization direction corresponding to the target voltage adjustment amount is in-phase; If the adjustment direction of the target voltage adjustment amount is reverse, the phase synchronization direction corresponding to the target voltage adjustment amount is reverse.

6. The voltage regulation method according to claim 1, characterized in that: The step of sequentially adjusting the amplitude of each phase voltage according to the phase synchronization direction of each phase voltage, the absolute value of each target voltage adjustment amount, and the preset adjustment step of the off-grid inverter includes: Determine whether to perform voltage compensation on each phase voltage according to the absolute value of each target voltage adjustment amount; If so, the adjustment interval of each phase voltage is determined according to the phase synchronization direction of each phase voltage, and the amplitude of each phase voltage is adjusted in sequence according to the adjustment interval of each phase voltage and the preset adjustment step of the off-grid inverter.

7. The voltage regulation method according to claim 6, characterized in that: The step of determining the adjustment interval of each phase voltage according to the phase synchronization direction of each phase voltage, and adjusting the amplitude of each phase voltage in sequence according to the adjustment interval of each phase voltage and the preset adjustment step of the off-grid inverter includes: If the phase synchronization directions of the phase voltages of the various phases are all in phase, then the amplitudes of the phase voltages are adjusted in sequence according to the preset adjustment step of the off-grid inverter; If at least one of the phase synchronization directions of the phase voltages is in reverse phase, the amplitude of the phase voltages is adjusted in sequence according to the preset adjustment step of the off-grid inverter. After waiting for a preset time, the phase is flipped, and then the amplitude of the phase voltages is adjusted in sequence according to the preset adjustment step of the off-grid inverter.

8. The voltage regulation method according to claim 1, characterized in that: The power quality control system further includes: a first power conversion unit, a second power conversion unit and a detection and monitoring module; the first power conversion unit and the second power conversion unit are connected to a three-phase power grid, the output end of the first power conversion unit is respectively connected to the input end of the second power conversion unit and the off-grid inverter, the detection and monitoring module is respectively connected to the first power conversion unit, the second power conversion unit and the off-grid inverter in communication, and the method further includes: The first power conversion unit provides direct current to the second power conversion unit and the off-grid inverter under the control of the detection and monitoring module; The second power conversion unit adjusts the output power of the three-phase power grid under the control of the detection and monitoring module.

9. A power conversion module, characterized in that: The power conversion module is used to implement the steps of the voltage regulation method described in any one of claims 1-8.

10. A power quality control system, characterized in that: The power quality control system comprises: a transformer module, a switch module, a detection and monitoring module and the power conversion module according to claim 9, wherein the power conversion module comprises: a first power conversion unit, a second power conversion unit and an off-grid inverter; One end of the transformer module is connected to the three-phase power grid, and the other end of the transformer module is connected to the AC port of the off-grid inverter in the power conversion module; The AC port of the first power conversion unit and the AC port of the second power conversion unit are both connected to the three-phase power grid, and the DC port of the first power conversion unit is connected to the off-grid inverter and the DC port of the second power conversion unit respectively; The AC port of the off-grid inverter is also connected to the switch module, and the detection and monitoring module is respectively connected to the transformer module and the power conversion module for communication.

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