Power decoupling control method and system and three-phase unified power quality conditioner

Abstract

The invention relates to a power decoupling control method, a power decoupling control system and a three-phase unified power quality regulator. The method comprises the following steps: acquiring real-time voltages at two sides of a direct-current side support capacitor; processing the real-time voltage through a preset power decoupling ring to obtain a target voltage; calculating a difference value between the target voltage and the capacitor reference voltage, and performing PI control on the difference value to obtain a parallel side current instruction value; calculating a reference current value of a parallel side filter inductor according to the parallel side current instruction value and the parallel side compensation current instruction value; and processing the reference current value and the real-time current value of the parallel side filter inductor based on a proportional integral resonance controller to obtain a first modulated wave signal. By decoupling the power control of the series side and the parallel side, the influence of the DC side voltage ripple on the UPQC compensation effect is greatly reduced, no extra circuit needs to be added, the capacitance value of the DC side support capacitor is effectively reduced, and the equipment cost and size are saved.

Description

Technical Field

[0001] The present application relates to the field of circuit control technology, and in particular to a power decoupling control method, system and a three-phase unified power quality conditioner. Background Art

[0002] With the advancement of modern industrial technology, a large number of power electronic devices and sensitive loads are used in power systems, which makes power users have higher and higher requirements for power quality. In addition, the startup of large equipment and the access of distributed power sources in the power system make the power supply voltage transient faults frequent; and the harmonic currents generated by nonlinear loads such as arc furnaces and power electronic devices cause great pollution to the power grid and reduce the power factor.

[0003] The three-phase unified power quality controller (UPQC) based on the DC side support capacitor has the ability to compensate for both grid-side voltage and load-side current. It can suppress voltage unbalance fluctuations, compensate for power quality problems such as voltage drops and voltage harmonics, and compensate for power quality problems such as reactive power and harmonic current caused by nonlinear loads.

[0004] However, due to the nonlinear load, the three-phase UPQC system has 5, 7, 11, and 13 pulsations in the instantaneous power on the parallel side, which will cause 6 and 12 power pulsations on the DC side. At the same time, if the unbalanced voltage fluctuations on the grid side are to be dealt with, the positive sequence current and unbalanced voltage of the series side converter will cause double frequency power pulsations on the DC side. The above pulsating power introduces a large DC ripple in the DC voltage or current, which affects the stability, waveform quality, and compensation effect of the series and parallel links. The existing scheme suppresses this by increasing the support capacitor or resonant branch and other passive power decoupling solutions, which will increase the equipment cost and volume. Summary of the invention

[0005] Based on this, it is necessary to provide a power decoupling control method, system and three-phase unified power quality conditioner to address the above technical problems without adding additional circuits and directly avoid the influence of power pulsation on the control performance of the series-parallel side converter in UPQC.

[0006] In a first aspect, the present application provides a power decoupling control method, which is applied to a three-phase unified power quality conditioner, wherein the three-phase unified power quality conditioner includes a three-phase AC power supply, a nonlinear load, a series transformer, a series side converter, a parallel side converter, a series side filter circuit, a parallel side filter circuit, and a DC side support capacitor, wherein one end of the primary side of the series transformer is connected to the three-phase AC power supply, and the other end of the primary side is connected to the nonlinear load, the secondary side of the series transformer adopts a triangle connection, and the secondary side of the series transformer is connected to the series side converter through the series side filter circuit, the series side converter is connected to the parallel side converter through the DC side support capacitor, and the parallel side converter is connected to the nonlinear load through the parallel side filter circuit;

[0007] The method comprises:

[0008] Collecting the real-time voltage on both sides of the DC side support capacitor;

[0009] Processing the real-time voltage through a preset power decoupling loop to obtain a target voltage;

[0010] Calculating the difference between the target voltage and the capacitor reference voltage, and performing PI control on the difference to obtain a parallel side current command value;

[0011] Calculating a reference current value of the parallel side filter inductor according to the parallel side current command value and the parallel side compensation current command value;

[0012] The reference current value and the real-time current value of the parallel side filter inductor are processed based on a proportional-integral resonant controller to obtain a first modulation wave signal, wherein the first modulation wave signal is used to adjust the switching state of the power tube in the parallel side converter.

[0013] In one embodiment, the method further comprises:

[0014] Calculate the target capacitance value of the DC side support capacitor according to the topological structure of the three-phase unified power quality conditioner and the pulsation power calculation formula of the series-parallel side converter;

[0015] The actual capacitance value of the DC side support capacitor is set to the target capacitance value.

[0016] In one embodiment, the method further comprises:

[0017] A preset sinusoidal pulse width modulation strategy of the series side converter is executed according to the target capacitance value.

[0018] In one embodiment, the step of processing the real-time voltage by a preset power decoupling loop to obtain a target voltage includes:

[0019] The real-time voltage is processed based on a preset notch filter transfer function to perform zero-static error control on a DC pulsating component in the real-time voltage to obtain the target voltage, wherein the DC pulsating component is calculated from the DC side output power of the series converter and the DC side output power of the parallel converter.

[0020] In the second aspect, the present application also provides a power decoupling control system, which is applied to a three-phase unified power quality conditioner, wherein the three-phase unified power quality conditioner includes a three-phase AC power supply, a nonlinear load, a series transformer, a series side converter, a parallel side converter, a series side filter circuit, a parallel side filter circuit, and a DC side support capacitor, wherein one end of the primary side of the series transformer is connected to the three-phase AC power supply, and the other end of the primary side is connected to the nonlinear load, the secondary side of the series transformer adopts a triangle connection, and the secondary side of the series transformer is connected to the series side converter through the series side filter circuit, the series side converter is connected to the parallel side converter through the DC side support capacitor, and the parallel side converter is connected to the nonlinear load through the parallel side filter circuit;

[0021] The system comprises:

[0022] A collection module, used for collecting the real-time voltage on both sides of the DC side support capacitor;

[0023] A decoupling loop processing module, used for processing the real-time voltage through a preset power decoupling loop to obtain a target voltage;

[0024] A first calculation module, used for calculating the difference between the target voltage and the capacitor reference voltage, and performing PI control on the difference to obtain a parallel side current command value;

[0025] A second calculation module, used for calculating a reference current value of the parallel side filter inductor according to the parallel side current command value and the parallel side compensation current command value;

[0026] The first modulation module is used to process the reference current value and the real-time current value of the parallel side filter inductor based on a proportional-integral resonant controller to obtain a first modulation wave signal, wherein the first modulation wave signal is used to adjust the switching state of the power tube in the parallel side converter.

[0027] In one embodiment, the system further comprises:

[0028] A capacitor configuration module is used to calculate the target capacitance value of the DC side support capacitor according to the topological structure of the three-phase unified power quality conditioner and the pulsating power calculation formula of the series-parallel side converter; and set the actual capacitance value of the DC side support capacitor to the target capacitance value.

[0029] In one embodiment, the system further comprises:

[0030] The second modulation module is used to execute a preset sinusoidal pulse width modulation strategy of the series-side converter according to the target capacitance value.

[0031] In a third aspect, the present application further provides a three-phase unified power quality conditioner, including a three-phase AC power supply, a nonlinear load, a series transformer, a series-side converter, a parallel-side converter, a series-side filter circuit, a parallel-side filter circuit, and a DC-side support capacitor;

[0032] One end of the primary side of the series transformer is connected to the three-phase AC power supply, and the other end of the primary side is connected to the nonlinear load. The secondary side of the series transformer adopts a triangle connection method, and the secondary side of the series transformer is connected to the series side converter through the series side filter circuit, the series side converter is connected to the parallel side converter through the DC side support capacitor, and the parallel side converter is connected to the nonlinear load through the parallel side filter circuit;

[0033] The parallel-side converter performs switch modulation using the power decoupling control method described in the first aspect.

[0034] In one of the embodiments, the actual capacitance value of the DC side support capacitor is a target capacitance value, wherein the target capacitance value is calculated based on the topological structure of the three-phase unified power quality conditioner and the pulsating power calculation formula of the series-parallel side converter.

[0035] In one of the embodiments, the series side converter executes a preset sinusoidal pulse width modulation strategy according to the target capacitance value.

[0036] In summary, the present application proposes a power decoupling control method, system and three-phase unified power quality conditioner, including: collecting the real-time voltage on both sides of the DC side support capacitor; processing the real-time voltage through a preset power decoupling loop to obtain the target voltage; calculating the difference between the target voltage and the capacitor reference voltage, and performing PI control on the difference to obtain the parallel side current command value; calculating the reference current value of the parallel side filter inductor according to the parallel side current command value and the parallel side compensation current command value; processing the reference current value and the real-time current value of the parallel side filter inductor based on the proportional integral resonant controller to obtain a first modulation wave signal. The present invention greatly reduces the influence of the DC side voltage ripple on the UPQC compensation effect by decoupling the power control of the series side and the parallel side, without adding additional circuits, effectively reducing the capacitance of the DC side support capacitor, and saving equipment cost and volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1A circuit diagram of a three-phase unified power quality conditioner in one embodiment;

[0038] Figure 2 is a schematic flow chart of a power decoupling control method in one embodiment;

[0039] Figure 3 A schematic diagram of calculation of a modulation strategy of a parallel-side converter after adding a power loop in one embodiment;

[0040] Figure 4 A schematic diagram of a flow chart of steps for calculating a target capacitor in one embodiment;

[0041] Figure 5 FIG. 4 is a structural block diagram of a power decoupling control device in an embodiment. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0043] like Figure 1 As shown, a three-phase three-wire unified power quality controller (Unified Power Quality Conditioner, UPQC for short) circuit is provided, including: a three-phase AC power supply, a nonlinear load, a series transformer, a series side converter (Series Converter, SEC for short), a shunt side converter (Shunt Converter, SHC for short), a series side filter circuit, a shunt side filter circuit and a DC side support capacitor.

[0044] Specifically, Figure 1 As shown, the three-phase AC power supply includes a three-phase voltage output terminal , and One end of the primary side of the series transformer is connected to a three-phase AC power supply, and the other end of the primary side is connected to a nonlinear load. The secondary side of the series transformer is connected in a triangle manner, and the secondary side of the series transformer is connected to the series side converter SEC through a series side filter circuit. The series side converter SEC is connected to the DC side support capacitor The parallel side converter SHC is connected, and the parallel side converter SHC is connected to a nonlinear load through a parallel side filter circuit.

[0045] In this embodiment, the series side filter circuit includes a series side filter inductor , and , series side filter capacitor , and The parallel side filter circuit includes a parallel side filter inductor , , , , and , parallel side filter capacitor , and .

[0046] The triangle connection of the secondary side of the series transformer can effectively cope with the voltage asymmetry drop compensation condition on the three-phase three-wire UPQC grid side, that is, the three-phase AC power supply side. In actual application, UPQC has the ability to compensate for grid-side voltage and load-side current, which can suppress voltage unbalance fluctuations, compensate for voltage drops and voltage harmonics and other power quality problems, and can also compensate for power quality problems such as reactive power and harmonic current caused by nonlinear loads.

[0047] In this embodiment, the series side filter inductor and the series side filter capacitor form an LC filter structure, and the parallel side filter inductor and the parallel side filter capacitor form an LCL filter structure, which respectively filter the outputs of the series side converter SEC and the parallel side converter SHC.

[0048] DC side support capacitor The positive and negative ends of the DC output side of the series-side converter SEC and the parallel-side converter SHC are respectively connected to maintain a constant self-sufficient DC voltage and realize flexible compensation of grid voltage fluctuations and harmonic conditions on the series-parallel side.

[0049] In this embodiment, the series-side three-phase converter SEC, LC filter and series-side transformer function as a series-type dynamic voltage regulator (DVR) to compensate for the voltage fluctuation condition on the grid side. The parallel-side three-phase converter SHC and LCL filter realize the function of an active power filter (APF) to compensate for current harmonics and reactive power compensation caused by nonlinear loads.

[0050] This embodiment provides a power decoupling control method, which adds a power decoupling loop to the control strategy of the parallel-side converter SHC and introduces the actual capacitor voltage into the modulation strategy of the series converter, so as to achieve the suppression effect of the pulsating power on the DC side on both sides of the UPQC and weaken the coupling influence of the series-parallel side converters.

[0051] In one embodiment, Figure 2 As shown, a power decoupling control method is provided, which is applied to Figure 1 The three-phase unified power quality conditioner in the example is used to illustrate, including the following steps:

[0052] S201, collecting real-time voltages on both sides of the DC side support capacitor.

[0053] In this embodiment, if Figure 1 As shown, the real-time voltage on both sides of the DC side support capacitor is .

[0054] In this embodiment, the power decoupling control method on the three sides of UPQC (DC side, series side, parallel side) must meet the following requirements: ,in, is the pulsating power on the DC side, is the DC side output power of the parallel side converter, is the DC side output power of the series side converter.

[0055] S202, processing the real-time voltage through a preset power decoupling loop to obtain a target voltage.

[0056] In this embodiment, since the parallel-side converter needs to compensate for the 5th, 7th, 11th, and 13th current harmonics caused by the nonlinear load of the system, the instantaneous power on the parallel side will have 5th, 7th, 11th, and 13th pulsations, and the voltage drop of the DC-side supporting capacitor includes 6th and 12th power pulsations. In order to cope with the unbalanced fluctuation of the grid voltage, the positive sequence current of the series-side converter and the unbalanced capacitor voltage will cause a double frequency power pulsation on the DC side.

[0057] In this embodiment, a preset power decoupling loop is added to the control strategy of the parallel-side converter SHC. , using the preset power decoupling loop The parallel side current command value does not contain the pulsating component on the DC side, which can effectively achieve series-parallel power decoupling. The output value of is the target voltage.

[0058] In a feasible embodiment, according to the Internal Model Principle (IMP for short), the power decoupling loop may use a notch filter to suppress the AC quantity of a specific frequency.

[0059] In one embodiment, the real-time voltage is processed by a preset power decoupling loop to obtain a target voltage, including:

[0060] The real-time voltage is processed based on a preset notch filter transfer function to perform zero-static error control on a DC pulsating component in the real-time voltage to obtain a target voltage, wherein the DC pulsating component is calculated by the DC side output power of the series converter and the DC side output power of the parallel converter.

[0061] In this embodiment, the preset notch filter transfer function is: ,in, is a complex frequency variable, is the pulsation angular frequency, where , is the damping of the feedforward branch.

[0062] In a specific embodiment, The smaller the value, the better the notch characteristics of the notch filter, but the frequency adaptability will become worse. When setting the value, it is necessary to compromise between the notch effect, frequency adaptability and the dynamic response of the feedforward branch.

[0063] In this embodiment, the target voltage is .

[0064] S203, calculating the difference between the target voltage and the capacitor reference voltage, and performing PI control on the difference to obtain a parallel side current command value.

[0065] In this embodiment, according to the power decoupling loop Output target voltage With capacitor reference voltage By calculating the difference and then performing PI control on the difference, the parallel side current command value can be obtained.

[0066] In this embodiment, if Figure 3 As shown, according to the target voltage With capacitor reference voltage Calculate the difference After that, according to the DC voltage loop By performing PI control on the difference, the parallel side current command value can be obtained.

[0067] In this embodiment, the parallel side current command value is = .

[0068] S204, calculating a reference current value of the parallel side filter inductor according to the parallel side current command value and the parallel side compensation current command value.

[0069] In this embodiment, the parallel side compensation current command value is obtained by extracting the harmonic content in the current of the three-phase AC power supply with nonlinear load. Specifically, a bandpass filter in a rotating dq coordinate system can be used to extract multiple harmonics to obtain the harmonic content and .

[0070] Specifically, the expression for multi-harmonic extraction using the bandpass filtering method is:

[0071]

[0072] in, is the resonant angular frequency, is the cut-off angular frequency. Using the resonant frequency The bandpass filter extracts the harmonic components in the load current. Among them, , .

[0073] like Figure 3 As shown, according to the parallel side current command value and parallel side compensation current command value The reference current value of the corresponding parallel side filter inductor can be calculated .

[0074] S205, based on the proportional-integral resonant controller, processes the reference current value and the real-time current value of the parallel-side filter inductor to obtain a first modulation wave signal, wherein the first modulation wave signal is used to adjust the switching state of the power tube in the parallel-side converter.

[0075] In this embodiment, according to the reference current value And the real-time current value of the parallel side filter inductor By performing PIR control, a three-phase modulated wave signal can be obtained. , and , i.e., the first modulation wave signal. The switching state of the power tube in the parallel side converter is adjusted according to the first modulation wave signal, thus completing the modulation strategy for the parallel side converter. Among them, the actual type of the power tube may be an insulated gate bipolar transistor (IGBT).

[0076] In this embodiment, a control strategy of a power decoupling loop is added to the basic control strategy of the parallel side converter SHC. Figure 3 The parallel-side converter adopts DC voltage outer loop and AC current inner loop control, aiming at controlling and compensating harmonic current and stabilizing voltage.

[0077] In this embodiment, the control equation of the AC current inner loop control can be expressed as:

[0078]

[0079] in, is a phase-locked loop PI regulator, is the control output of the DC voltage loop, and is the capacitor voltage component of the parallel-side converter, and is the real-time inductor current component of the parallel side converter.

[0080] In this embodiment, the DC voltage loop Using PI controller, AC current loop Using the PIR controller, the PI controller transfer function and the PIR controller transfer function are:

[0081]

[0082] in, is the voltage loop proportional term coefficient, is the current loop proportional term coefficient, is the voltage loop integral coefficient, is the current loop integral coefficient, is the resonant term coefficient of the current loop.

[0083] In summary, this embodiment provides a power decoupling control method, which can achieve active power decoupling by directly changing the control strategy of the UPQC parallel-side converter without adding additional circuits. The power decoupling control method proposed in this embodiment can effectively reduce the DC-side support capacitor capacitance while reducing the impact of DC-side voltage ripple, avoiding the impact of power pulsation on the control performance of the series-parallel-side converter in UPQC, and avoiding the deterioration of system performance and power quality caused by the interaction between the AC and DC sides.

[0084] In one embodiment, if Figure 4 As shown, the power decoupling control method also includes:

[0085] S401, calculating a target capacitance value of a DC side support capacitor according to a topological structure of a three-phase unified power quality conditioner and a pulsating power calculation formula of a series-parallel side converter;

[0086] S402, setting the actual capacitance value of the DC side support capacitor to the target capacitance value.

[0087] In this embodiment, if Figure 1 As shown in the figure, according to the topological structure of the three-phase unified power quality conditioner, the power formula of the series-parallel side can be clearly .

[0088] DC side voltage It can be expressed as a constant With a small ripple voltage Addition:

[0089]

[0090] in, is the allowable DC side ripple peak value of the system. DC side capacitor current:

[0091]

[0092] Another expression for the capacitor current can be obtained from the power relationship:

[0093]

[0094] Then we get the specific expression of capacitor current:

[0095]

[0096] According to the above expression of capacitor current, the required value of DC side capacitor can be calculated:

[0097]

[0098] In this embodiment, by reducing the support capacitance The capacitance value can verify the effectiveness of the power decoupling method. In the specific verification process, the three-phase AC grid is set to 311V and the DC voltage is 750V, AC voltage frequency 50Hz, switching frequency 10kHz.

[0099] The measured current harmonic distortion rate with nonlinear load is 28.2%. If the DC ripple is 0.5%, the required DC capacitance is calculated to be 4000μF. At this time, the grid-side current harmonic distortion rate is 2.73% after compensation by the UPQC basic control strategy.

[0100] A power decoupling loop is added to the parallel-side converter control strategy. After increasing the DC ripple to 10%, the required DC capacitance is calculated to be 200 μF. At this time, the grid-side current harmonic distortion rate is 2.08% after compensation by the UPQC power decoupling control strategy proposed in this embodiment.

[0101] In one embodiment, the power decoupling control method further includes:

[0102] A preset sinusoidal pulse width modulation strategy of the series side converter is executed according to the target capacitance value.

[0103] In a specific embodiment, the modulation strategy determines how the converter generates an output signal according to an input signal. Introducing the target capacitance value as a reference for the modulation strategy can more effectively control the output of the converter, thereby reducing the impact of power pulsation on the DC side.

[0104] It should be noted that the specific implementation of the preset sinusoidal pulse width modulation strategy of the series side converter can refer to the modulation strategy for the series converter in the prior art. The power decoupling control method in this embodiment is to use the target capacitance value as a reference quantity for the preset sinusoidal pulse width modulation strategy of the series side converter.

[0105] In summary, this embodiment provides a power decoupling control method, which does not require additional circuits to be added on the basis of the three-phase UPQC topology structure, and uses the DC side support capacitor to absorb DC ripple. In addition, by adding an active power decoupling link in the control strategy of the parallel side converter of the three-phase unified power quality conditioner, and introducing the actual capacitor voltage in the series converter modulation strategy, the UPQC can effectively suppress the DC side pulsating power on both sides and weaken the coupling effect of the series-parallel side converter. The compensation requirements of UPQC are met while greatly reducing the capacitance value of the support capacitor.

[0106] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0107] Based on the same inventive concept, the embodiment of the present application also provides a power decoupling control system for implementing the power decoupling control method involved above. The implementation scheme for solving the problem provided by the system is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more power decoupling control system embodiments provided below can refer to the limitations on the power decoupling control method above, and will not be repeated here.

[0108] In one embodiment, Figure 5 As shown, a power decoupling control system 500 is provided, comprising: an acquisition module 510, a decoupling loop processing module 520, a first calculation module 530, a second calculation module 540 and a first modulation module 550, wherein:

[0109] The acquisition module 510 is used to acquire the real-time voltage on both sides of the DC side support capacitor;

[0110] A decoupling loop processing module 520 is used to process the real-time voltage through a preset power decoupling loop to obtain a target voltage;

[0111] A first calculation module 530 is used to calculate the difference between the target voltage and the capacitor reference voltage, and perform PI control on the difference to obtain a parallel side current command value;

[0112] A second calculation module 540, configured to calculate a reference current value of the parallel side filter inductor according to the parallel side current command value and the parallel side compensation current command value;

[0113] The first modulation module 550 is used to process the reference current value and the real-time current value of the parallel side filter inductor based on the proportional-integral resonant controller to obtain a first modulation wave signal, wherein the first modulation wave signal is used to adjust the switching state of the power tube in the parallel side converter.

[0114] In one embodiment, the power decoupling control system 500 further includes:

[0115] The capacitor configuration module is used to calculate the target capacitance value of the DC side support capacitor according to the topological structure of the three-phase unified power quality conditioner and the pulsation power calculation formula of the series-parallel side converter; and set the actual capacitance value of the DC side support capacitor to the target capacitance value.

[0116] In one embodiment, the power decoupling control system 500 further includes:

[0117] The second modulation module is used to execute a preset sinusoidal pulse width modulation strategy of the series-side converter according to a target capacitance value.

[0118] In summary, this embodiment provides a power decoupling control system, which does not need to add additional circuits on the basis of the three-phase UPQC topology structure, and uses the DC side support capacitor to absorb DC ripple. In addition, by adding an active power decoupling link in the control strategy of the parallel side converter of the three-phase unified power quality conditioner, and introducing the actual capacitor voltage in the series converter modulation strategy, the UPQC can effectively suppress the DC side pulsating power on both sides and weaken the coupling effect of the series-parallel side converter. The compensation requirements of UPQC are met while greatly reducing the capacitance value of the support capacitor.

[0119] Each module in the above power decoupling control system can be implemented in whole or in part by software, hardware, or a combination thereof. Each module can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to each module.

[0120] In one embodiment, a computer device is provided, comprising the decoupling control system in the foregoing embodiment.

[0121] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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.

[0122] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A power decoupling control method, characterized in that: Applicable to a three-phase unified power quality conditioner, wherein the three-phase unified power quality conditioner includes a three-phase AC power supply, a nonlinear load, a series transformer, a series-side converter, a parallel-side converter, a series-side filter circuit, a parallel-side filter circuit and a DC-side support capacitor, wherein one end of the primary side of the series transformer is connected to the three-phase AC power supply, and the other end of the primary side is connected to the nonlinear load, the secondary side of the series transformer adopts a triangle connection method, and the secondary side of the series transformer is connected to the series-side converter through the series-side filter circuit, the series-side converter is connected to the parallel-side converter through the DC-side support capacitor, and the parallel-side converter is connected to the nonlinear load through the parallel-side filter circuit; The method comprises: Collecting the real-time voltage on both sides of the DC side support capacitor; Processing the real-time voltage through a preset power decoupling loop to obtain a target voltage; Calculating the difference between the target voltage and the capacitor reference voltage, and performing PI control on the difference to obtain a parallel side current command value; Calculating a reference current value of the parallel side filter inductor according to the parallel side current command value and the parallel side compensation current command value; The reference current value and the real-time current value of the parallel side filter inductor are processed based on a proportional-integral resonant controller to obtain a first modulation wave signal, wherein the first modulation wave signal is used to adjust the switching state of the power tube in the parallel side converter.

2. The method according to claim 1, characterized in that The method further comprises: Calculate the target capacitance value of the DC side support capacitor according to the topological structure of the three-phase unified power quality conditioner and the pulsation power calculation formula of the series-parallel side converter; The actual capacitance value of the DC side support capacitor is set to the target capacitance value.

3. The method according to claim 2, characterized in that The method further comprises: A preset sinusoidal pulse width modulation strategy of the series side converter is executed according to the target capacitance value.

4. The method according to claim 1, characterized in that: The step of processing the real-time voltage by a preset power decoupling loop to obtain a target voltage includes: The real-time voltage is processed based on a preset notch filter transfer function to perform zero-static error control on a DC pulsating component in the real-time voltage to obtain the target voltage, wherein the DC pulsating component is calculated from the DC side output power of the series converter and the DC side output power of the parallel converter.

5. A power decoupling control system, characterized in that: Applicable to a three-phase unified power quality conditioner, wherein the three-phase unified power quality conditioner includes a three-phase AC power supply, a nonlinear load, a series transformer, a series-side converter, a parallel-side converter, a series-side filter circuit, a parallel-side filter circuit and a DC-side support capacitor, wherein one end of the primary side of the series transformer is connected to the three-phase AC power supply, and the other end of the primary side is connected to the nonlinear load, the secondary side of the series transformer adopts a triangle connection method, and the secondary side of the series transformer is connected to the series-side converter through the series-side filter circuit, the series-side converter is connected to the parallel-side converter through the DC-side support capacitor, and the parallel-side converter is connected to the nonlinear load through the parallel-side filter circuit; The system comprises: A collection module, used for collecting the real-time voltage on both sides of the DC side support capacitor; A decoupling loop processing module, used for processing the real-time voltage through a preset power decoupling loop to obtain a target voltage; A first calculation module, used for calculating the difference between the target voltage and the capacitor reference voltage, and performing PI control on the difference to obtain a parallel side current command value; A second calculation module, used for calculating a reference current value of the parallel side filter inductor according to the parallel side current command value and the parallel side compensation current command value; The first modulation module is used to process the reference current value and the real-time current value of the parallel side filter inductor based on a proportional-integral resonant controller to obtain a first modulation wave signal, wherein the first modulation wave signal is used to adjust the switching state of the power tube in the parallel side converter.

6. The system according to claim 5, characterized in that The system further comprises: A capacitor configuration module is used to calculate the target capacitance value of the DC side support capacitor according to the topological structure of the three-phase unified power quality conditioner and the pulsating power calculation formula of the series-parallel side converter; and set the actual capacitance value of the DC side support capacitor to the target capacitance value.

7. The system according to claim 6, characterized in that The system further comprises: The second modulation module is used to execute a preset sinusoidal pulse width modulation strategy of the series-side converter according to the target capacitance value.

8. A three-phase unified power quality conditioner, characterized in that: It includes a three-phase AC power supply, a nonlinear load, a series transformer, a series side converter, a parallel side converter, a series side filter circuit, a parallel side filter circuit and a DC side support capacitor; One end of the primary side of the series transformer is connected to the three-phase AC power supply, and the other end of the primary side is connected to the nonlinear load. The secondary side of the series transformer adopts a triangle connection method, and the secondary side of the series transformer is connected to the series side converter through the series side filter circuit, the series side converter is connected to the parallel side converter through the DC side support capacitor, and the parallel side converter is connected to the nonlinear load through the parallel side filter circuit; The parallel-side converter performs switch modulation using the power decoupling control method described in any one of claims 1 to 4.

9. The three-phase unified power quality conditioner according to claim 8, characterized in that: The actual capacitance value of the DC side support capacitor is the target capacitance value, wherein the target capacitance value is calculated according to the topological structure of the three-phase unified power quality conditioner and the pulsating power calculation formula of the series-parallel side converter.

10. The three-phase unified power quality conditioner according to claim 9, characterized in that: The series side converter executes a preset sinusoidal pulse width modulation strategy according to the target capacitance value.

Images