Integrated multifunctional power quality treatment device and control strategy thereof

Abstract

The application provides an integrated multifunctional power quality treatment device and a control strategy thereof, and belongs to the field of electrical engineering; the problems of single function and low integration of the power quality treatment device are solved; the specific control strategy is as follows: the voltage and phase of a power grid are acquired, and the given current and actual current of d-axis and q-axis are calculated; the given current and actual current of each phase on the d-axis and q-axis are subtracted and superposed with the voltage feedforward, so that the modulation wave of each phase on the parallel side is obtained; the given value and actual compensation voltage of the compensation voltage of each phase on the series side are subtracted and superposed with the voltage feedforward, so that the modulation wave of each phase on the series side is output; the modulation waves of each phase on the parallel side and the series side are decoupled, so that the driving signal of the power regulating device is generated; through the three-bridge-arm multiplexing topology and the control strategy of multiple modes of common mode, the application integrates the voltage and current power quality comprehensive treatment function, simplifies the equipment structure, reduces the cost loss, and improves the power grid working condition adaptability and power device utilization rate.

Description

Technical Field

[0001] This invention relates to an integrated multifunctional power quality management device and its control strategy, belonging to the field of electrical engineering. Background Technology

[0002] With the increasing penetration of nonlinear loads and distributed photovoltaic power sources in low-voltage distribution networks, power quality issues are becoming increasingly prominent. This is not only manifested in the reduction of power factor and increase of line losses caused by reactive power and harmonic pollution, but also more prominently in voltage quality problems such as voltage sags, voltage rises, and three-phase voltage imbalances, which seriously affect the normal operation of user equipment.

[0003] To comprehensively address power quality issues, the traditional approach typically involves installing multiple single-function power electronic devices. Examples include static var generators (SVG), active power filters (APF), or dynamic voltage restorers (DVRs). However, this method of multiple devices operating independently has drawbacks such as large footprint, high investment costs, and complex system coordination and control.

[0004] Unified Power Quality Conditioner (UPQC) is a recognized comprehensive compensation solution that can simultaneously address voltage and current quality issues. Traditional UPQCs typically employ a back-to-back dual converter structure, consisting of a series-side converter and a parallel-side converter connected via a DC bus capacitor.

[0005] Although traditional UPQCs possess good comprehensive compensation capabilities, they still have limitations in practical low-voltage distribution network applications. Traditional UPQCs require two independent inverters, along with corresponding drive and protection circuits and output filters. This results in higher overall cost and larger size for the device. Under normal grid voltage conditions, the series-side inverter remains in standby or light-load mode for extended periods, only operating at full load under abnormal conditions such as voltage dips, leading to low utilization of its power devices.

[0006] Therefore, how to simplify the hardware topology of UPQC, reduce manufacturing costs, ensure its ability to quickly and effectively manage voltage problems, and improve the overall utilization rate of power devices are the technical problems that urgently need to be solved in the field of power quality management of low-voltage distribution networks. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an integrated multifunctional power quality management device and its control strategy, thereby solving the problems of limited functionality and low integration in existing power quality management devices.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: A control strategy for an integrated multifunctional power quality management device includes: Obtain the voltage and phase of the power grid; calculate the d-axis given current by subtracting the actual voltage of the DC bus from the voltage setpoint; calculate the q-axis given current, process the actual compensation currents of phases A, B, and C, and obtain the actual currents of phases A, B, and C on the d-axis and q-axis; calculate the difference between the given currents and actual currents of phases A, B, and C on the d-axis and q-axis and superimpose the power grid voltage feedforward to obtain the parallel-side modulation wave of phases A, B, and C; Obtain the load voltages corresponding to A, B, and C, and calculate the difference between the grid voltage and the load voltage as the given value of the series-side compensation voltage; obtain the actual compensation voltages corresponding to the series sides of A, B, and C, calculate the difference between the given value of the series-side compensation voltage of each phase and the actual compensation voltage, and superimpose the voltage feedforward to output the series-side modulation waves corresponding to A, B, and C. Based on the parallel-side modulation waves and series-side modulation waves of phases A, B, and C, constraint equations for the corresponding bridge arm port voltages of phases A, B, and C are constructed. The modulation waves of the parallel and series sides are decoupled to obtain the modulation waves of the first, second, and third bridge arms, and drive signals for controlling the power devices are generated.

[0009] Furthermore, the calculation steps for the parallel-side modulated wave are as follows: Obtain the phase voltages of phases A, B, and C of the power grid to obtain the phase voltage. Phase voltage Phase voltage ; Construct the orthogonal components of phase A voltage along the α and β axes to obtain... and ; Obtain the fundamental phase angle of phase A voltage of the power grid ,right and Perform a Park transform to obtain the voltage feedforward components of phase A grid voltage on the d-axis and q-axis. and ; Obtain the voltage setpoint of phase A DC bus With actual voltage ,calculate and difference ; Will Input to the PI controller to obtain the given current for the d-axis current of phase A. ; Determine if the q-axis current of phase A has a given value, and calculate the given q-axis current of phase A. .

[0010] Furthermore, the calculation steps for the parallel-side modulated wave also include: Obtain the actual compensation current of phase A Construct orthogonal components and ; For current and Perform the Park transformation to obtain the actual d-axis and q-axis currents of phase A. and ; Obtain the given values ​​of active and reactive current in phase A. and ; Calculate the compensation current difference between the given and actual values ​​of the active and reactive currents of phase A, and obtain... and ; Will and Input to the PI controller to obtain the primary control voltages for the d-axis and q-axis of phase A. and ; Will and Add them together, and Adding them together, we obtain the control voltages of phase A along the d-axis and q-axis. and ; With phase angle Based on, for and Perform an inverse Park transform to obtain the modulated wave at the parallel port of phase A. ; Generate the modulation wave at the parallel port of phase B and phase C. and .

[0011] Furthermore, The calculation steps are as follows: Scenario 1: If there is a given value for the q-axis current of phase A, then no action is taken; Scenario 2: If there is no given value for the q-axis current of phase A, then determine whether there is a given value for the reactive power of phase A; if so, calculate the given current of the q-axis of phase A based on the given value of the reactive power of phase A. ; Scenario 3: If there is no given value for the q-axis current of phase A and the given value for the reactive power of phase A, then obtain the load current corresponding to phase A. With phase angle Based on the reference, extract the load current. The load reactive component is used to obtain the given current of phase A's q-axis. .

[0012] Furthermore, the calculation steps for the series-modulated wave are as follows: Obtain the load voltage and phase voltage corresponding to phases A, B, and C, and calculate the setpoint values ​​of the series-side compensation voltages corresponding to phases A, B, and C. , and ; Obtain the actual compensation voltages on the corresponding series sides of the three phases A, B, and C, and get , and ; Calculate the compensation voltage deviation on the series side sequentially. , and ; Deviation The basic control voltages on the series side of phase A are obtained by inputting them into the fundamental, third, and fifth resonant controllers, respectively. ; Phase A voltage After filtering, the feedforward quantity of the series-connected voltage of phase A is obtained. ; Will and Adding them together yields the modulated wave on the series side of phase A. ; Generate the modulated wave at the parallel port of phase B and phase C, and obtain and .

[0013] Furthermore, the steps for generating the drive signal are as follows: The steps for generating drive signals are as follows: Obtain the modulation waves of the corresponding parallel ports of phases A, B, and C. , and Modulated wave at the series port , and ; Construct constraint equations for the corresponding bridge arm port voltages of phases A, B, and C, resulting in equations A, B, and C: Equation A: ; in, , and , respectively representing the modulation waves of the first bridge arm, the second bridge arm, and the third bridge arm in the device corresponding to A; Set the value selection strategy for the second bridge arm in the device corresponding to A, and calculate the modulation reference wave of the first, second and third bridge arms of the device corresponding to A; Based on the modulation reference waves of the first, second, and third bridge arms of the corresponding device A, a high-frequency triangular carrier signal with a fixed frequency and symmetrical amplitude is generated. The frequency of this carrier signal is higher than the fundamental frequency of the power grid.

[0014] Furthermore, the step of generating the drive signal also includes: Point-by-point comparison of the modulated wave of the first bridge arm of phase A with the triangular carrier wave: When the instantaneous value of the A-phase modulation wave is greater than the instantaneous value of the triangular carrier wave, the upper tube of the first bridge arm is turned on and the lower tube is turned off. When the instantaneous value of the A-phase modulation wave is less than the instantaneous value of the triangular carrier wave, the lower tube of the first bridge arm is turned on and the upper tube is turned off. If the instantaneous value of the A-phase modulated wave is equal to the instantaneous value of the triangular carrier wave, then determine whether the triangular carrier wave is on the rising or falling edge, and perform a switching operation: When the rising edge of the triangular carrier reaches the intersection, a dead zone is inserted. Subsequent carriers are larger than the modulated wave, and the lower tube is switched on. When the falling edge of the triangular carrier reaches the intersection, a dead zone is inserted. Subsequent carriers are smaller than the modulated wave, and the upper tube is switched on. Based on the comparison results between the modulation wave of the first bridge arm of phase A and the triangular carrier wave, a set of PWM pulse sequences with duty cycles varying with the amplitude of the modulation wave are generated for the first bridge arm. The PWM pulse sequence of the second and third bridge arms of phase A is generated to obtain the switching drive signal for controlling the corresponding power device of phase A; Generate switching drive signals to control the power devices corresponding to phase B and phase C.

[0015] Furthermore, the value selection strategy for the second bridge arm includes: Strategy 1: Symmetric bias strategy; Temporary common mode The value is set to ;in, This represents the actual voltage of the DC bus in phase A; Calculate the temporary bridge arm modulation waves of the first to third bridge arms to obtain , and ; extract , , The maximum and minimum values ​​in the range are obtained. and Calculate common mode ; Will As Substitute the value of the equation into equation A and calculate. and ; Strategy 2: Fixed DC strategy; make The value is Substitute into equation A and calculate and The value; Strategy 2 allows for the superposition of communication components: Compare and The amplitude is selected, and the modulation wave with the larger amplitude is chosen as the fundamental wave. ; Obtain the angular frequency of the fundamental wave of the power grid Constructing AC components ; Will sequentially with the original , and Adding them together, we obtain the new modulated waves of the first, second, and third bridge arms of the corresponding device A.

[0016] Furthermore, the value selection strategy for the second bridge arm also includes: Strategy 3: No-communication diversion strategy; make The value is Substitute into equation A and calculate and The value; , and No communication component; Strategy 4: Minimize switching losses; Common mode The domain is set to Construct the cost function ; ; According to the modulated wave and Real-time changes are assessed using the minimum absolute deviation estimation algorithm to calculate the cost function. Minimum common modulus, calculation , and The value of .

[0017] An integrated multifunctional power quality management device includes: Three bridge arms: first bridge arms Q1 and Q3, second bridge arms Q2 and Q4, and third bridge arms Q5 and Q6; The second bridge arm serves as a common bridge arm for both the parallel and series sides; Parallel side: Composed of the first and second bridge arms, paired with a parallel filter inductor L f1 Parallel connection on the grid side Ug ; Series side: The second and third bridge arms together form a series filter inductor L. f2 With series compensation capacitor C f2 Connected in series in the power grid U g and load R L middle.

[0018] Compared with the prior art, the beneficial effects of the present invention are: The invention adopts a three-arm reuse hardware topology to reduce the number of power devices: The integrated multi-functional power quality management device of the present invention adopts a three-arm reuse topology structure. By reusing the common arm, it realizes the integration of grid-side current management and load-side voltage management functions, reducing the number of power devices such as power switching tubes, drive circuits, and filter inductors, thus compressing the overall size and weight of the device. It can be adapted to various application scenarios such as embedded installation in distribution cabinets.

[0019] Multiple switchable common-mode control strategies: This invention sets four selectable common-mode voltage solution strategies, including symmetrical bias, fixed DC, no AC component in the common arm, and minimum switching loss optimization strategy. Different strategies can be flexibly switched according to the actual operating conditions on site, solving the problem that traditional power quality management devices have a single control mode and cannot balance voltage utilization and device losses as needed.

[0020] Three-phase independent governance architecture: The basic unit of this device is a single-phase three-bridge arm multiplexed power quality governance unit. When it can be expanded into a three-phase system, it adopts a hardware-control architecture with independent A, B and C phases. Each phase is equipped with a complete set of single-phase three-bridge arm hardware and corresponding control algorithm. The sampling signals, phase-locked phases and common-mode solution processes of each phase are decoupled from each other. There is no control coupling problem between the three phases. It has a strong ability to manage three-phase voltage imbalance and current imbalance. Attached Figure Description

[0021] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the single-phase power quality management device of the present invention; Figure 2 This is a schematic diagram of the three-phase power quality improvement device of the present invention; Figure 3 This is a schematic diagram of the control process of the power quality management device of the present invention; Figure 4 This is a schematic diagram of the control strategy of the present invention. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] Please see Figure 1 An integrated multifunctional power quality management device includes: Three bridge arms: first bridge arm (Q1 and Q3), second bridge arm (Q2 and Q4), and third bridge arm (Q5 and Q6). Nodes a, b, and c represent the output endpoints of the first bridge arm, the second bridge arm, and the third bridge arm, respectively. The second bridge arm serves as a common bridge arm for both the parallel and series sides; Parallel side: Composed of the first and second bridge arms, paired with a parallel filter inductor L f1 Parallel connection on the grid side U g ; Series side: The second and third bridge arms together form a series filter inductor L. f2 With series compensation capacitor C f2 Connected in series in the power grid U g and load R L middle; i a U represents the compensation current of the parallel branch. cf This represents the compensation voltage for the series branch.

[0025] Figure 1 In the circuit diagram, the wire connecting the upper ends of Q1, Q2, and Q5 together is the DC positive bus; the wire connecting the lower ends of Q3, Q4, and Q6 together is the DC negative bus; the DC positive bus and the DC negative bus together constitute the DC bus, and the capacitor connected in parallel between the DC positive bus and the DC negative bus is the DC bus capacitor.

[0026] Please see Figure 2 An integrated multi-functional power quality management device (three-phase) also includes: The parallel filter inductor L of phases A, B, and C f1 L f3 With L f5 Series filter inductor L f2 L f4 With L f6 ; The series compensation capacitor C for phases A, B, and C. fa C fb With C fc The load R of the three phases A, B, and C LA R LB With R LC; It should be noted that, unless otherwise specified, the term "device" in this invention refers to "an integrated multi-functional power quality management device".

[0027] Example 2

[0028] Please see Figure 3 and Figure 4 A control strategy for an integrated multifunctional power quality management device includes: It should be noted that, Figure 3 In This indicates the grid voltage, corresponding to the phase voltages of phases A, B, and C in the subsequent grid. Figure 3 In and These represent the voltage feedforward components of the grid voltage on the d-axis and q-axis, respectively; Figure 3 In Indicates the DC bus voltage. This represents the given value of the DC bus voltage; Figure 3 In Indicates the compensation current. This indicates the feedback quantity of the d-axis compensation current (corresponding to the actual compensation current). This represents the given value of the d-axis compensation current; Figure 3 In Indicates the compensation current. This indicates the feedback quantity of the q-axis compensation current (corresponding to the actual compensation current). This represents the given value of the q-axis compensation current; Figure 3 In Indicates the modulated wave on the parallel side; Figure 3 In Indicates the load voltage. This represents the actual compensation voltage on the series side. This indicates voltage feedforward on the series side. This indicates the output of the PR controller (where PR controller 1, 2, and 3 represent the fundamental, 3rd, and 5th resonant controllers, respectively). Figure 3 In This indicates a series-modulated wave.

[0029] Step S1: Generate the parallel-side modulated wave; Obtain the grid voltage and use a SOGI second-order generalized integrator and PLL phase-locked loop to obtain the phase of the grid voltage; calculate the difference between the actual voltage of the DC bus and the voltage setpoint, and obtain the d-axis setpoint current through a PI controller; calculate the q-axis setpoint current, and use a SOGI second-order generalized integrator and Park transform to process the actual compensation current of the three phases A, B, and C on the parallel filter inductor to obtain the actual current of the three phases A, B, and C on the d-axis and q-axis; The given currents and actual currents of phases A, B, and C on the d-axis and q-axis are subtracted and superimposed with the grid voltage feedforward. The inverse Park transform is then used to obtain the parallel-side modulation wave of phases A, B, and C. The specific steps of step S1 are as follows: Obtain the phase voltages of phases A, B, and C of the power grid to obtain the phase voltage. Phase voltage Phase voltage ; Generate the modulation wave at the parallel port of phase A. ; Phase voltage By inputting a second-order generalized integrator (SOGI), orthogonal components of the phase voltage of phase A along the α-axis and β-axis (i.e., the two-phase stationary coordinate system) are constructed, and the following results are obtained. and ; Will and Input a PLL (phase-locked loop) to obtain the fundamental phase angle of phase A voltage in the power grid. ; With phase angle Based on, for and Performing the Park transform, we obtain the voltage feedforward components of phase A grid voltage on the d-axis and q-axis, denoted as... and ; ; ; Obtain the voltage setpoint of phase A DC bus With actual voltage ,calculate and difference , ; Will Input to the PI controller to obtain the given current for the d-axis current of phase A. ; Determine if the q-axis current of phase A has a given value, and calculate the given q-axis current of phase A. ; Scenario 1: If there is a given value for the q-axis current of phase A, then no processing is required (i.e., the given value for the q-axis current of phase A is directly obtained). Scenario 2: If there is no given value for the q-axis current of phase A, then determine whether there is a given value for the reactive power of phase A; if so, calculate the given current of the q-axis of phase A based on the given value of the reactive power of phase A. ; The given value for obtaining the reactive power of phase A is Calculate the given current of phase A's q-axis. : ; Scenario 3: If there is no given value for the q-axis current of phase A and the given value for the reactive power of phase A, then obtain the load current corresponding to phase A. With phase angle Based on the reference, extract the load current. The load reactive component is used to obtain the given current of phase A's q-axis. ; load current Input the SOGI second-order generalized integrator to construct the load current. The orthogonal components along the α-axis and β-axis are obtained. and ; With phase angle Based on, for and Perform the Park transformation to obtain the active current of phase A load current. With reactive current ; ; ; The reactive current of phase A load current The given current as the d-axis current of phase A ,Right now ; Obtain the actual compensation current of phase A A second-order generalized integrator of SOGI is used to construct a compensation current. The orthogonal components along the α-axis and β-axis are obtained. and ; with phase angle As a reference, for current and Performing the Park transformation yields the actual d-axis and q-axis currents of phase A, denoted as... and ; ; ; in, It also indicates the actual active current of phase A. It also represents the actual reactive current of phase A; Obtain the given values ​​of active and reactive current in phase A. and ; Calculate the compensation current difference between the given and actual values ​​of the active and reactive currents of phase A, and obtain... and ; ; ; Will and Inputting the PI controller yields the primary control voltages for the A-phase d-axis and q-axis, denoted as... and ; Will and Add them together, and Adding them together, we obtain the control voltages of phase A along the d-axis and q-axis. and ; With phase angle Based on, for and Performing the inverse Park transform, we obtain the orthogonal components of the A-phase control voltage along the α and β axes, denoted as... and ; ; ; Will Modulation wave as the parallel side port of phase A ; Repeatedly generate the modulation wave at the parallel port of phase A. The steps involve generating the modulated wave at the parallel port of phase B and phase C to obtain... and .

[0030] Step S2: Generate the series-modulated wave; Obtain the corresponding load voltages A, B, and C, and calculate the difference between the grid voltage and the load voltage as the given value for the series-side compensation voltage. Obtain the actual compensation voltages of the corresponding series sides of phases A, B, and C. Calculate the difference between the given value of the compensation voltage on the series side of each phase and the actual compensation voltage, input the difference into the multi-PR controller group, and then superimpose the voltage feedforward to output the corresponding series side modulation waves of phases A, B, and C.

[0031] The specific steps of step S2 are as follows: Obtain the corresponding load voltages A, B, and C to get , and ; Obtain the phase voltages of phases A, B, and C of the power grid to obtain the phase voltage. Phase voltage Phase voltage ; Calculate in sequence and , and and pressure and The difference is used to obtain the given values ​​of the compensation voltages on the corresponding series sides of the three phases A, B, and C. , and ; Obtain the actual compensation voltages on the corresponding series sides of the three phases A, B, and C, and get , and ; Calculate in sequence and , and as well as and The difference is used to obtain the deviation of the compensation voltage on the corresponding series side of the three phases A, B, and C, which is denoted as deviation. , and ; Deviation The voltage is copied three times and input into a multi-PR controller group consisting of the fundamental, 3rd, and 5th resonant controllers respectively, to obtain the basic control voltage on the series side of phase A. ; The fundamental frequency PR controller only affects the deviation. The 50Hz fundamental component is amplified and adjusted to eliminate the steady-state error of the fundamental voltage, resulting in a corrected output. ; The 3rd harmonic PR controller only amplifies the deviation. The third harmonic component is used to cancel the third harmonic voltage, resulting in a corrected output. ; The 5th harmonic PR controller only amplifies the deviation. The 5th harmonic component is used to cancel the 5th harmonic voltage, resulting in a corrected output. ; Will , and Adding them together, we obtain the basic control voltage on the series side of phase A. ; Use digital filters (such as second-order Butterworth low-pass digital filters (IIR), first-order inertial low-pass filters, etc.) to filter the phase voltage of phase A. Perform filtering to remove phase voltage. The high-frequency noise and switching frequency interference in the AD sampling are eliminated, and the fundamental frequency of 50Hz and the components of the 3rd and 5th harmonics are retained to obtain the feedforward quantity of the series side voltage of phase A. ; Will and Added together, as the modulation wave on the series side of phase A. ; Repeatedly generate the modulation wave on the series side of phase A. The steps involve generating the modulated wave at the parallel port of phase B and phase C to obtain... and .

[0032] Step S3: Output the switching drive signal for the power device; Based on the parallel and series modulation waves of phases A, B, and C, constraint equations for the corresponding bridge arm port voltages of phases A, B, and C are constructed. The modulation waves of the parallel and series sides are decoupled to obtain the modulation waves of the first, second, and third bridge arms. SPWM is used to generate the IGBT drive pulse signal to regulate the switching state of the power devices. Obtain the modulation waves of the corresponding parallel ports of phases A, B, and C. , and Modulated wave at the series port , and ; Construct constraint equations for the corresponding bridge arm port voltages of phases A, B, and C, resulting in equations A, B, and C: Equation A: ; in, , and , respectively representing the modulation waves of the first bridge arm, the second bridge arm, and the third bridge arm in the device corresponding to A; Equation B: ; in, , and , respectively representing the modulation waves of the first bridge arm, the second bridge arm and the third bridge arm in the device corresponding to B; Equation C: ; in, , and , respectively representing the modulation waves of the first bridge arm, the second bridge arm and the third bridge arm in the device corresponding to C; Set the value selection strategy for the second bridge arm in the corresponding device of A, and generate the switching drive signal to control the corresponding power device of A; Strategy 1: Symmetrical bias strategy (applicable scenario: maximizing voltage utilization); Temporary common mode The value is set to ,Right now ;in, This represents the actual voltage of the DC bus in phase A; It should be noted that common mode means the same offset that is simultaneously superimposed on the first bridge arm, the second bridge arm, and the third bridge arm; Calculate the temporary bridge arm modulation waves of the first to third bridge arms to obtain , and ; in, ; ; ; extract , , The maximum and minimum values ​​in the range are obtained. and ; Calculate common mode ; Will As Substitute the value of the equation into equation A and calculate. and ; ; ; Strategy 2: Fixed DC strategy (Applicable scenarios: no special requirements, most common); make The value is Substitute into equation A and calculate and The value; ; ; Strategy 2 allows for the superposition of communication components: Branch 21: Superimposed third harmonic; Compare and The amplitude is selected, and the modulation wave with the larger amplitude is chosen as the fundamental wave. ; Obtain the angular frequency of the fundamental wave of the power grid Constructing AC components : Where t represents time; Will sequentially with the original , and Adding them together, we obtain the new modulated waves of the first, second, and third bridge arms of the device corresponding to A, denoted as , and ; ; ; ; Branch 22: Dynamically optimize common mode; Within each DSP control cycle, acquire and Instantaneous value, obtained and ; make The instantaneous value ,calculate and The instantaneous value is obtained. and ; in, ; ; Calculate AC components : ; AC components are obtained through deformation. : ; Will sequentially with the original , and Adding them together, we obtain the new modulated waves of the first, second, and third bridge arms of the device corresponding to A; Strategy 3: No AC shunt strategy (applicable scenario: minimizing the switching loss of the second bridge arm). make The value is Substitute into equation A and calculate and The value; ; ; , and No communication component; Strategy 4: Minimize switching losses (Applicable scenario: Minimize the total switching losses of the device). Common mode The domain is set to Construct the cost function : ; According to the modulated wave and Real-time changes are calculated using the Least-Absolute-Deviation (LAD) algorithm to determine the cost function. To find the minimum common modulus, based on the existing common modulus, repeat the calculation process of strategy 1. , and The value; Different strategies are selected based on the actual usage scenario of the device to calculate the modulation reference wave of the first, second, and third bridge arms of the device corresponding to A. Based on the modulation reference waves of the first, second, and third bridge arms of the corresponding device A, a high-frequency triangular carrier signal with a fixed frequency and symmetrical amplitude is generated. The frequency of this carrier signal is higher than the fundamental frequency of the power grid. Point-by-point comparison of the modulated wave of the first bridge arm of phase A with the triangular carrier wave: When the instantaneous value of the A-phase modulation wave is greater than the instantaneous value of the triangular carrier wave, the upper tube of the first bridge arm is turned on and the lower tube is turned off. When the instantaneous value of the A-phase modulation wave is less than the instantaneous value of the triangular carrier wave, the lower tube of the first bridge arm is turned on and the upper tube is turned off. If the instantaneous value of the A-phase modulated wave is equal to the instantaneous value of the triangular carrier wave, it indicates that the intersection point has been reached. Then, determine whether the triangular carrier wave is on its rising or falling edge, and perform a switching operation. When the rising edge of the triangular carrier wave (i.e., the carrier wave moves upward from small to large) reaches the intersection point, a dead zone is inserted. Subsequent carrier waves are larger than the modulated wave, and the lower tube is switched on. When the triangular carrier falls (i.e., the carrier moves from large to small downwards), after reaching the intersection point, a dead zone is inserted. Subsequent carriers are smaller than the modulated wave, and the upper tube is switched on.

[0033] The aforementioned dead zone indicates that when a bridge arm switch state transition occurs, a waiting time is inserted between "one tube being turned off" and "the other tube being turned on" to force both tubes to turn off; the value range of the dead zone is 1 to 5 microseconds, preferably 2 microseconds or 2.5 microseconds; Based on the comparison result between the modulation wave of the first bridge arm of phase A and the triangular carrier wave, a set of PWM pulse sequences with duty cycles varying with the amplitude of the modulation wave are generated for the first bridge arm. The average voltage of this sequence is proportional to the instantaneous value of the modulation wave of the corresponding phase. Repeat the steps of generating the PWM pulse sequence of the first bridge arm of phase A to generate the PWM pulse sequences of the second and third bridge arms of phase A; The PWM pulse sequences of the first to third bridge arms of phase A are summarized and used as the switching drive signals to control the corresponding power devices in phase A; Repeat the steps of generating the switching drive signals for the power devices corresponding to phase A, and generate the switching drive signals for the power devices corresponding to phases B and C.

[0034] Compared to the problems described in the background art, the present invention adopts a three-bridge-arm reused topology to replace the traditional back-to-back dual converter UPQC hardware architecture. By reusing the common bridge arm, the hardware integration of series-side voltage management and parallel-side current management functions is achieved, reducing the number of inverters, drive circuits and filter devices, alleviating the problems of redundancy of traditional UPQC devices, high overall cost and large size, and improving the overall utilization rate of power devices. Furthermore, this invention sets up a variety of switchable common-mode voltage control strategies, flexibly selecting symmetrical bias, fixed DC bias, common arm without AC component constraint, and minimum switching loss optimization strategy according to the actual operating conditions of the distribution network. It balances voltage utilization, common arm switching loss, and total system loss as needed, solving the shortcomings of the traditional UPQC control mode being single and unable to adapt to diverse operating conditions, and taking into account both the reliability and energy efficiency of the device. Furthermore, this invention relies on the SOGI second-order generalized integrator to construct virtual orthogonal components, and adopts a hierarchical closed-loop architecture that combines parallel-side dq dual closed-loop PI control with grid voltage feedforward and series-side multi-resonant PR control to achieve DC bus voltage stabilization, harmonic suppression, reactive power compensation, and rapid voltage disturbance mitigation, thereby improving the system's dynamic response and steady-state compensation accuracy.

[0035] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementation methods. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The present invention is limited only to the technical solutions and their full scope and equivalents.

Claims

1. A control strategy for an integrated multifunctional power quality management device, characterized in that, Control strategies include: Obtain the voltage and phase of the power grid; calculate the d-axis given current by subtracting the actual voltage of the DC bus from the voltage setpoint; calculate the q-axis given current, process the actual compensation currents of phases A, B, and C, and obtain the actual currents of phases A, B, and C on the d-axis and q-axis; calculate the difference between the given currents and actual currents of phases A, B, and C on the d-axis and q-axis and superimpose the power grid voltage feedforward to obtain the parallel-side modulation wave of phases A, B, and C; Obtain the load voltages corresponding to A, B, and C, and calculate the difference between the grid voltage and the load voltage as the given value of the series-side compensation voltage; obtain the actual compensation voltages corresponding to the series sides of A, B, and C, calculate the difference between the given value of the series-side compensation voltage of each phase and the actual compensation voltage, and superimpose the voltage feedforward to output the series-side modulation waves corresponding to A, B, and C. Based on the parallel-side modulation waves and series-side modulation waves of phases A, B, and C, constraint equations for the corresponding bridge arm port voltages of phases A, B, and C are constructed. The modulation waves of the parallel and series sides are decoupled to obtain the modulation waves of the first, second, and third bridge arms, and drive signals for controlling the power devices are generated.

2. The control strategy of the integrated multifunctional power quality management device according to claim 1, characterized in that, The calculation steps for the parallel-side modulated wave are as follows: Obtain the phase voltages of phases A, B, and C of the power grid to obtain the phase voltage. Phase voltage Phase voltage ; Construct the orthogonal components of phase A voltage along the α and β axes to obtain... and ; Obtain the fundamental phase angle of phase A voltage of the power grid ,right and Perform a Park transform to obtain the voltage feedforward components of phase A grid voltage on the d-axis and q-axis. and ; Obtain the voltage setpoint of phase A DC bus With actual voltage ,calculate and difference ; Will Input to the PI controller to obtain the given current for the d-axis current of phase A. ; Determine if the q-axis current of phase A has a given value, and calculate the given q-axis current of phase A. .

3. The control strategy of the integrated multifunctional power quality management device according to claim 2, characterized in that, The calculation steps for the parallel-side modulated wave also include: Obtain the actual compensation current of phase A Construct orthogonal components and ; For current and Perform the Park transformation to obtain the actual d-axis and q-axis currents of phase A. and ; Obtain the given values ​​of active and reactive current in phase A. and ; Calculate the compensation current difference between the given and actual values ​​of the active and reactive currents of phase A, and obtain... and ; Will and Input to the PI controller to obtain the primary control voltages for the d-axis and q-axis of phase A. and ; Will and Add them together, and Adding them together, we obtain the control voltages of phase A along the d-axis and q-axis. and ; With phase angle Based on, for and Perform an inverse Park transform to obtain the modulated wave at the parallel port of phase A. ; Generate the modulation wave at the parallel port of phase B and phase C. and .

4. The control strategy of the integrated multifunctional power quality management device according to claim 2, characterized in that, The calculation steps are as follows: Scenario 1: If there is a given value for the q-axis current of phase A, then no action is taken; Scenario 2: If there is no given value for the q-axis current of phase A, then determine whether there is a given value for the reactive power of phase A; if so, calculate the given current of the q-axis of phase A based on the given value of the reactive power of phase A. ; Scenario 3: If there is no given value for the q-axis current of phase A and the given value for the reactive power of phase A, then obtain the load current corresponding to phase A. With phase angle Based on the reference, extract the load current. The load reactive component is used to obtain the given current of phase A's q-axis. .

5. The control strategy of the integrated multifunctional power quality management device according to claim 1, characterized in that, The calculation steps for the series-modulated wave are as follows: Obtain the load voltage and phase voltage corresponding to phases A, B, and C, and calculate the setpoint values ​​of the series-side compensation voltages corresponding to phases A, B, and C. , and ; Obtain the actual compensation voltages on the corresponding series sides of the three phases A, B, and C, and get , and ; Calculate the compensation voltage deviation on the series side sequentially. , and ; Deviation The voltage is copied three times and input into the fundamental, 3rd, and 5th resonant controllers respectively to obtain the basic control voltage on the series side of phase A. ; Phase A voltage After filtering, the feedforward quantity of the series-connected voltage of phase A is obtained. ; Will and Adding them together yields the modulated wave on the series side of phase A. ; Generate the modulated wave at the parallel port of phase B and phase C, and obtain and .

6. The control strategy of the integrated multifunctional power quality management device according to claim 1, characterized in that, The steps for generating drive signals are as follows: Obtain the modulation waves of the corresponding parallel ports of phases A, B, and C. , and Modulated wave at the series port , and ; Construct constraint equations for the corresponding bridge arm port voltages of phases A, B, and C, resulting in equations A, B, and C: Equation A: ； in, , and , respectively representing the modulation waves of the first bridge arm, the second bridge arm, and the third bridge arm in the device corresponding to A; Set the value selection strategy for the second bridge arm in the device corresponding to A, and calculate the modulation reference wave of the first, second and third bridge arms of the device corresponding to A; Based on the modulation reference waves of the first, second, and third bridge arms of the corresponding device A, a high-frequency triangular carrier signal with fixed frequency and symmetrical amplitude is generated.

7. The control strategy of the integrated multifunctional power quality management device according to claim 6, characterized in that, The steps for generating drive signals also include: Point-by-point comparison of the modulated wave of the first bridge arm of phase A with the triangular carrier wave: When the instantaneous value of the A-phase modulation wave is greater than the instantaneous value of the triangular carrier wave, the upper tube of the first bridge arm is turned on and the lower tube is turned off. When the instantaneous value of the A-phase modulation wave is less than the instantaneous value of the triangular carrier wave, the lower tube of the first bridge arm is turned on and the upper tube is turned off. If the instantaneous value of the A-phase modulated wave is equal to the instantaneous value of the triangular carrier wave, then determine whether the triangular carrier wave is on the rising or falling edge, and perform a switching operation: When the rising edge of the triangular carrier reaches the intersection, a dead zone is inserted. Subsequent carriers are larger than the modulated wave, and the lower tube is switched on. When the falling edge of the triangular carrier reaches the intersection, a dead zone is inserted. Subsequent carriers are smaller than the modulated wave, and the upper tube is switched on. Based on the comparison results between the modulation wave of the first bridge arm of phase A and the triangular carrier wave, a set of PWM pulse sequences with duty cycles varying with the amplitude of the modulation wave are generated for the first bridge arm. Generate PWM pulse sequences for the second and third bridge arms of phase A to obtain the switching drive signals for controlling the corresponding power devices in phase A; Generate switching drive signals to control the power devices corresponding to phase B and phase C.

8. The control strategy of the integrated multifunctional power quality management device according to claim 6, characterized in that, The value selection strategy for the second bridge arm includes: Strategy 1: Symmetric bias strategy; Temporary common mode The value is set to ;in, This represents the actual voltage of the DC bus in phase A; Calculate the temporary bridge arm modulation waves of the first to third bridge arms to obtain , and ; extract , , The maximum and minimum values ​​in the range are obtained. and Calculate common mode ; Will As Substitute the value of the equation into equation A and calculate. and ; Strategy 2: Fixed DC strategy; make The value is Substitute into equation A and calculate and The value; Strategy 2 allows for the superposition of communication components: Compare and The amplitude is selected, and the modulation wave with the larger amplitude is chosen as the fundamental wave. ; Obtain the angular frequency of the fundamental wave of the power grid Constructing AC components ; Will sequentially with the original , and Adding them together, we obtain the new modulated waves of the first, second, and third bridge arms of the corresponding device A.

9. The control strategy of the integrated multifunctional power quality management device according to claim 8, characterized in that, The value selection strategy for the second bridge arm also includes: Strategy 3: No-communication diversion strategy; make The value is Substitute into equation A and calculate and The value; , and No communication component; Strategy 4: Minimize switching losses; Common mode The domain is set to Construct the cost function ; ； According to the modulated wave and Real-time changes are assessed using the minimum absolute deviation estimation algorithm to calculate the cost function. Minimum common modulus, calculation , and The value of .

10. An integrated multifunctional power quality management device, applicable to the control strategy of the integrated multifunctional power quality management device according to any one of claims 1-9, characterized in that, Power quality management devices include: Three bridge arms: first bridge arms Q1 and Q3, second bridge arms Q2 and Q4, and third bridge arms Q5 and Q6; The second bridge arm serves as a common bridge arm for both the parallel and series sides; Parallel side: Composed of the first and second bridge arms, paired with a parallel filter inductor L f1 Parallel connection on the grid side U g ; Series side: The second and third bridge arms together form a series filter inductor L. f2 With series compensation capacitor C f2 Connected in series in the power grid U g and load R L middle.

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