Energy storage and electric energy quality integrated system and control method thereof

Abstract

The invention discloses an energy storage and electric energy quality integrated system and a control method thereof. The system is characterized in that the direct current end of a UPQC series compensation converter, the direct current end of a UPQC parallel compensation converter and an energy storage battery module are all connected to a unified direct current bus; the UPQC series compensation converter is connected to a power grid side through an isolation transformer; the UPQC parallel compensation converter is connected to a load side; and the power coordination controller is used for coordinately controlling the charging and discharging of the energy storage battery module according to the electrical parameters of the power grid side and the load side, and controlling the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter. According to the invention, the UPQC completely replaces a traditional energy storage PCS, so that the system has multi-dimensional power quality adjustment capabilities such as voltage treatment, three-phase imbalance compensation, harmonic treatment, sag support and the like, and an integrated architecture of energy storage and power quality comprehensive treatment is realized.

Description

An integrated energy storage and power quality system and its control method Technical Field

[0001] This invention relates to the fields of power quality management of distribution networks, grid-connected control of energy storage systems, and power conversion technology, and more specifically to an integrated energy storage power quality system and its control method. Background Technology

[0002] With the large-scale access of distributed photovoltaic power to distribution network areas, the following typical problems have emerged in the voltage of the distribution area: (1) High voltage exceeding the limit caused by photovoltaic backfeeding during the day; (2) Low voltage exceeding the limit caused by concentrated load at night; (3) Uneven distribution of residential loads leading to three-phase imbalance.

[0003] Existing industrial and commercial energy storage systems and distribution network energy storage systems typically use traditional bidirectional PCS (Power Conversion System) as the power interface between the battery and the grid. The PCS is mainly responsible for energy storage charging and discharging, grid-connected inversion, and basic reactive power regulation, but its capabilities in voltage over-limit management, flicker suppression, three-phase imbalance regulation, and harmonic filtering are limited.

[0004] UPQC (Unified Power Quality Conditioner) is a typical power quality management device, consisting of series and parallel compensators, capable of voltage compensation, harmonic control, and reactive power regulation. However, UPQC lacks its own energy storage device, and its compensation capability relies on grid energy, making it unsuitable for long-term voltage management scenarios.

[0005] At present, a small number of energy storage UPQC technologies on the market still maintain the main UPQC architecture, only adding energy storage modules on the DC side (i.e. the DC bus side inside UPQC). They have not formed a new grid-connected interface structure with energy storage system as the core, and cannot replace PCS, nor can they meet the needs of energy storage system for bidirectional energy flow control, SOC (State of Charge) management and long-term compensation.

[0006] Therefore, there is an urgent need for a new integrated energy storage structure that can natively integrate UPQC into the energy storage cabinet and completely replace PCS, so as to achieve the unification of charging and discharging control, power quality management and voltage regulation functions. Summary of the Invention

[0007] In view of the above problems, the present invention proposes an integrated energy storage and power quality system and its control method to overcome or at least partially solve the above problems.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, embodiments of the present invention provide an integrated energy storage and power quality system, comprising: an energy storage battery module, a unified DC bus, a UPQC series compensation converter, a UPQC parallel compensation converter, and a power coordination controller; the DC terminals of the UPQC series compensation converter, the UPQC parallel compensation converter, and the energy storage battery module are all connected to the unified DC bus; the UPQC series compensation converter is connected to the grid side via an isolation transformer; the UPQC parallel compensation converter is connected to the load side; the power coordination controller is communicatively connected to the UPQC series compensation converter, the UPQC parallel compensation converter, and the energy storage battery module, respectively, and is used to coordinate and control the charging and discharging of the energy storage battery module, and control the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter, based on the electrical parameters of the grid side and the load side.

[0009] Furthermore, it also includes a battery management system; the battery management system is connected between the energy storage battery module and the unified DC bus, and is communicatively connected to the power coordination controller.

[0010] Furthermore, it also includes a power quality monitoring module; the power quality monitoring module is used to collect electrical parameters of the grid side and the load side in real time and transmit them to the power coordination controller. The power coordination controller identifies the current power quality status based on the electrical parameters, generates corresponding voltage compensation commands and / or current compensation commands, and sends the voltage compensation commands to the UPQC series compensation converter and the current compensation commands to the UPQC parallel compensation converter.

[0011] Furthermore, the power coordination controller is also used to dynamically adjust the compensation magnitude of the voltage compensation command and / or current compensation command according to the state of charge value of the energy storage battery module; wherein: when the state of charge value is higher than a preset threshold, the system power is allocated in a manner that prioritizes meeting the power quality compensation requirements; when the state of charge value is lower than the preset threshold, the current compensation depth of the UPQC parallel compensation converter is reduced, and the system control objective is switched to maintain the grid connection point voltage stability as the primary objective.

[0012] Furthermore, the compensation action of the UPQC series compensation converter includes at least one of voltage sag support, overvoltage suppression, voltage flicker mitigation, and three-phase voltage imbalance regulation.

[0013] Furthermore, the compensation action of the UPQC parallel compensation converter includes at least one of harmonic current filtering, reactive power compensation, three-phase current imbalance regulation, and power factor correction.

[0014] Furthermore, the UPQC series compensation converter and the UPQC parallel compensation converter together constitute the only power conversion interface between the energy storage battery module and the AC power grid.

[0015] Secondly, the present invention provides a control method for an integrated energy storage and power quality system, applied to the aforementioned system, comprising the following steps: S1, acquiring electrical parameters on the grid side and the load side; S2, using a power coordination controller, coordinating and controlling the charging and discharging of the energy storage battery module according to the electrical parameters, and controlling the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter.

[0016] Further, in S2, the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter are controlled according to the electrical parameters. Specifically, the power coordination controller identifies the current power quality status according to the electrical parameters, generates corresponding voltage compensation commands and / or current compensation commands, and sends the voltage compensation commands to the UPQC series compensation converter and the current compensation commands to the UPQC parallel compensation converter.

[0017] Furthermore, it also includes: dynamically adjusting the compensation magnitude of the voltage compensation command and / or current compensation command based on the state of charge value of the energy storage battery module; wherein, when the state of charge value is higher than a preset threshold, the system power is allocated in a manner that prioritizes meeting the power quality compensation requirements; when the state of charge value is lower than the preset threshold, the current compensation depth of the UPQC parallel compensation converter is reduced, and the system control objective is switched to primarily maintaining the stability of the grid connection point voltage.

[0018] As can be seen from the above technical solution, compared with the prior art, the present invention discloses an integrated energy storage power quality system and its control method, which has the following beneficial effects: The present invention integrates the energy storage battery module with the UPQC series compensation converter and the UPQC parallel compensation converter through a unified DC bus, so that the compensation behavior has continuous energy support capability, overcomes the problem of traditional UPQC relying on filter capacitors and limited compensation time, realizes wide time scale compensation from millisecond to minute, and greatly improves the stability and reliability of voltage management.

[0019] This invention introduces a power coordination controller to realize real-time power allocation and priority management among energy storage charging and discharging, series voltage compensation, and parallel current compensation, avoiding command conflicts and energy offsets, enabling the system to maintain stable operation under multiple operating objectives, thereby significantly improving the system's coordinated regulation efficiency.

[0020] This invention enhances power quality management capabilities without altering the main structure of the energy storage cabinet. It eliminates the need for external SVG or voltage reduction and regulation equipment, allowing the energy storage system to directly replace multiple power quality management devices, reducing land occupation, simplifying system configuration, and lowering overall investment costs.

[0021] This invention utilizes the synergistic effect of parallel and series compensators to simultaneously eliminate negative sequence current, suppress harmonics, and regulate phase voltage deviation, achieving refined phase management that traditional PCS systems cannot accomplish. The system can maintain voltage within acceptable limits even in complex transformer substation scenarios with simultaneous low-voltage over-limit, high-voltage over-limit, and three-phase imbalance. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 is a schematic diagram of the integrated energy storage and power quality system framework provided in an embodiment of the present invention.

[0024] Figure 2 is a schematic diagram of the control method of the integrated energy storage and power quality system provided in the embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: This embodiment of the invention discloses an integrated energy storage and power quality system, as shown in Figure 1, comprising: an energy storage battery module, a unified DC bus, a UPQC series compensation converter, a UPQC parallel compensation converter, and a power coordination controller; wherein, the DC terminals of the UPQC series compensation converter, the UPQC parallel compensation converter, and the energy storage battery module are all connected to the unified DC bus; the UPQC series compensation converter is connected to the grid side through an isolation transformer; the UPQC parallel compensation converter is connected to the load side; the power coordination controller is communicatively connected to the UPQC series compensation converter, the UPQC parallel compensation converter, and the energy storage battery module, respectively, and is used to coordinate and control the charging and discharging of the energy storage battery module, and control the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter according to the electrical parameters of the grid side and the load side.

[0027] Next, each of the above parts will be explained in detail.

[0028] 1. Energy Storage Battery Module: The energy storage battery module is connected to the unified DC bus of the UPQC, providing stable DC energy support for both the series and parallel sides. In addition, a Battery Management System (BMS) is connected between the energy storage battery module and the unified DC bus; this BMS communicates with the power coordination controller and manages the charging and discharging states of the energy storage battery module under the control of the power coordination controller.

[0029] The energy storage battery module can use lithium iron phosphate, ternary lithium, or other electrochemical batteries suitable for energy storage scenarios. After being managed by the BMS, the energy storage battery is connected to a unified DC bus, forming the DC energy center of the energy storage system. Both the parallel compensation converter and the series compensation converter of the UPQC are connected to this unified DC bus, enabling the energy storage battery to directly provide energy for compensation activities and giving the system long-term compensation capability.

[0030] 2. Unified DC Bus: The unified DC bus connects the energy storage battery modules and the compensation converters, specifically including UPQC series compensation converters and UPQC parallel compensation converters, thus providing a common DC energy path for each converter unit. The DC voltage level of this unified DC bus can be configured according to the energy storage system capacity and grid connection voltage level, and its voltage range can be set to any reasonable range that meets the requirements of energy storage charging and discharging and power quality compensation operation.

[0031] 3. UPQC Series Compensation Converter and UPQC Parallel Compensation Converter: Structurally, this embodiment of the invention eliminates the traditional PCS, employing UPQC series and parallel converters as the sole power conversion interface between the energy storage battery module and the AC grid. Based on the rated power of the UPQC series and parallel compensation converters, the configuration is determined according to the sum of the maximum charging and discharging power of the energy storage system and the expected power quality compensation requirements, ensuring both long-term energy dispatch and transient power quality support. Unlike the existing technology of "UPQC supplementary energy storage," the UPQC itself in this embodiment serves as the power conversion unit of the energy storage cabinet, fundamentally changing the energy storage grid connection interface architecture and achieving deep integration of energy storage and power quality regulation.

[0032] On the grid-connected side, this embodiment of the invention employs a dual-inverter collaborative structure: a UPQC series compensator is connected to the grid side via an isolation transformer to compensate for voltage sags, overvoltages, voltage flicker, and three-phase voltage imbalances, achieving dynamic voltage regulation and stabilization. A UPQC parallel compensator is directly connected to the load side or grid connection point to compensate for harmonic currents, reactive power, current imbalances, and power factor, achieving real-time current management. At the control level, this invention adopts a unified power coordination control architecture. First, a power quality monitoring module is used to collect real-time data on three-phase voltage, current, frequency, and SOC status from both the grid and load sides, transmitting the collected electrical parameters to the power coordination controller. Second, the power coordination controller analyzes the grid operating status based on the electrical parameters, identifying the current power quality status type, including voltage exceeding limits, harmonic exceedances, three-phase imbalances, and transient disturbances. Finally, based on the current power quality status, corresponding voltage compensation commands and / or current compensation commands are generated, and the voltage compensation commands are sent to the UPQC series compensation converter, while the current compensation commands are sent to the UPQC parallel compensation converter.

[0033] 4. Power Coordination Controller: During the compensation command generation process, the power coordination controller performs coordinate transformation and component decoupling on the collected electrical parameters based on instantaneous power theory or dq coordinate transformation method, analyzes and obtains the active power component, reactive power component, harmonic component and negative sequence component to be compensated, and generates the corresponding voltage compensation command or current compensation command accordingly.

[0034] The system automatically allocates compensation tasks to the series and parallel sides based on compensation requirements. The allocation principle is as follows: when a voltage-related power quality problem is detected, the compensation task is preferentially assigned to the UPQC series compensation converter; when a current-related power quality problem is detected, the compensation task is preferentially assigned to the UPQC parallel compensation converter; when both voltage and current-related power quality problems exist simultaneously, the series and parallel compensation converters operate collaboratively, each undertaking the corresponding type of compensation task. Specifically, the UPQC series compensation converter is mainly used for voltage-related compensation, including at least one of voltage sag support, overvoltage suppression, voltage flicker mitigation, and three-phase voltage imbalance regulation. The UPQC parallel compensation converter is mainly used for current-related compensation, including at least one of harmonic current filtering, reactive power compensation, three-phase current imbalance regulation, and power factor correction.

[0035] In terms of energy storage and compensation coordination, this embodiment of the invention achieves energy sharing through unified DC bus management. Batteries can directly provide energy for the series-parallel compensation process, enabling the UPQC to provide long-term support in scenarios involving voltage over-limits or deep voltage sags, no longer limited by the transient compensation capabilities of traditional UPQCs. Specifically, the power coordination controller dynamically adjusts the compensation magnitude of voltage compensation commands and / or current compensation commands based on the state of charge (SOC) value of the energy storage battery modules. When the SOC value is higher than a preset threshold, system power is allocated to prioritize meeting power quality compensation requirements. When the SOC value is lower than the preset threshold, the current compensation depth for the UPQC parallel compensation converter is reduced, and the system control objective is switched to primarily maintaining grid connection voltage stability. Specifically, when the SOC is high, power quality management capabilities are prioritized; when the SOC is low, the deep compensation magnitude is reduced, switching to a basic voltage regulation mode. During bidirectional power flow operation, parallel coordinated control of energy storage charging / discharging and power quality compensation is achieved.

[0036] In summary, the integrated energy storage power quality system that replaces the traditional PCS with UPQC provided in this embodiment of the invention achieves unified deployment of functions such as energy storage charging and discharging control, voltage management, three-phase imbalance management, and harmonic compensation by reconstructing the power interface topology of the energy storage system.

[0037] This system supports dynamic switching between multiple modes, including: conventional energy storage charging and discharging mode, comprehensive power quality management mode, phase-by-phase control mode, rapid transient disturbance compensation mode, and off-grid / grid switching mode. The system can automatically enter the optimal operating mode based on load changes and distribution network conditions. For example, in a distribution area scenario where a composite problem of "low voltage in one phase and high voltage in another" occurs, the series side can boost or clip the voltage of the specific phase; the parallel side can provide negative sequence compensation for unbalanced current; and the energy storage side can simultaneously perform energy balancing, achieving unified management of phase voltage and phase power.

[0038] Through the deep integration of the aforementioned structure and control, this invention not only replaces the PCS for energy storage charging and discharging but also integrates all the power quality management capabilities of the UPQC, forming a novel "dual-purpose" energy storage device architecture. This significantly enhances the energy storage system's support for distribution network voltage quality and operational stability. Simultaneously, it effectively reduces the number of PCS, SVG, independent UPQC, and reactive power compensation devices required, significantly lowering system costs and footprint, and improving product competitiveness. This system is suitable for distribution network substations, industrial and commercial energy storage, and integrated photovoltaic-energy storage-charging power stations, demonstrating significant market promotion value and economic benefits.

[0039] Example 2: Based on Example 1 above, this embodiment of the invention sets the power quality monitoring module to use a high-speed sampling frequency of 10kHz–50kHz to monitor the three-phase voltage U on the grid side and the load side. a U Uc and three-phase current i a i Real-time data collection is performed using ICs.

[0040] By employing instantaneous power theory or the dq coordinate system transformation method, the acquired electrical parameters are subjected to coordinate transformation and component decoupling to obtain the following quantities: d-axis voltage and q-axis voltage, d-axis current and q-axis current, harmonic current components, unbalanced negative sequence current, voltage drop ΔU, and phase A voltage deviation ΔU in the synchronous rotating coordinate system (dq coordinate system). a Phase B voltage deviation ΔU The voltage deviation ΔUc between phase C and phase C.

[0041] Based on the above quantities, the power quality status can be dynamically determined, such as: voltage exceeding the upper / lower limit, harmonic current exceeding the limit, three-phase voltage imbalance, transient voltage disturbance, and peak-valley load impact. The monitoring module generates the following compensation instructions based on the above power quality status: current compensation instruction. Voltage compensation command DC bus power requirements SOC adjustment demand ΔSOC, A-phase power demand P a Phase B power requirement P And the C-phase power demand Pc. All reference quantities are entered into the power coordination controller for arbitration and calculation.

[0042] Example 3: Power Coordination Controller Coordination Strategy: Based on Example 2 above, this invention proposes the following coordination algorithm to simultaneously meet the requirements of energy storage scheduling, power quality management, DC bus stability, and compensation priority.

[0043] (1) Priority division: The system dynamically allocates priorities according to the grid status: Level 1: voltage drop / overvoltage compensation; Level 2: three-phase imbalance and voltage deviation management; Level 3: harmonic current compensation; Level 4: reactive power regulation; Level 5: energy storage normal charging and discharging; If a voltage drop of more than 10% is detected, the system will automatically use series compensation as the highest priority and suspend the normal operation of energy storage.

[0044] (2) DC bus power regulation: The power coordination controller collects the DC bus voltage Udc in real time and compares it with the preset reference voltage Udc_ref to obtain the DC bus voltage deviation ΔUdc, where ΔUdc = Udc Udc_ref is the rated operating voltage of the DC bus set by the system.

[0045] The power coordination controller adjusts the compensation command or compensation power allocation based on the DC bus voltage deviation ΔUdc and the battery SOC state: when ΔUdc < ΔUdc_min, the battery discharges to support the compensation energy; where ΔUdc_min is the minimum allowable negative deviation threshold of the DC bus voltage relative to the reference voltage; when ΔUdc > ΔUdc_max, the energy injected by the compensator is limited, and the battery is guided to absorb energy to keep the DC voltage stable during the compensation process; where ΔUdc_max is the maximum allowable positive deviation threshold of the DC bus voltage relative to the reference voltage.

[0046] (3) Series-parallel coordination: For voltage imbalance problems: the series side is used to adjust the phase voltage difference so that U a ≈U ≈Uc, the parallel side provides negative sequence current compensation, and the battery provides energy balance to avoid DC voltage deviation caused by unbalanced power flow; for grid harmonic issues: the parallel converter tracks the current compensation command through the current inner loop. The battery provides energy through the DC bus to offset transient energy fluctuations during harmonic injection.

[0047] (4) Integrated scheduling of energy storage and compensation: After the compensation demand is met, the excess power is used for energy storage charging; if there is a parallel demand for "compensation + discharge", the system prioritizes to meet the compensation demand, and then determines the discharge power according to the SOC and scheduling instructions.

[0048] Example 4, Typical Operating Scenario Description: Scenario 1: Low voltage on phase A and high voltage on phase C in the transformer area: The power quality monitoring module detected that the voltage U on phase A... a <0.9pu, C-phase voltage Uc>1.1pu, unbalanced current is relatively large.

[0049] The coordinated controller adopts the following strategies: 1) Series converter: raise phase A and clip phase C; 2) Parallel converter: compensate for negative sequence current; 3) Battery: provide / absorb energy to maintain the stability of the DC bus; 4) Phase-by-phase energy regulation: distribute battery energy to phases A / B / C as needed; ultimately achieving voltage recovery and elimination of phase imbalance.

[0050] Scenario 2: Heavy load impact + 20% voltage dip: The series compensator immediately injects compensation voltage to restore the bus voltage to its rated value. The parallel compensator absorbs the impact reactive power, and the battery provides the necessary active power within 100ms to maintain the DC side energy. The entire system maintains continuous operation without disconnecting from the grid.

[0051] Example 5: Based on the same inventive concept, this embodiment of the invention also provides a control method for an integrated energy storage power quality system, applied to the integrated energy storage power quality system in Example 1 above. As shown in Figure 2, the method includes: S1, acquiring electrical parameters on the grid side and the load side; specifically including three-phase voltage, three-phase current, frequency, and energy storage SOC state data; S2, through a power coordination controller, coordinating and controlling the charging and discharging of the energy storage battery module according to the electrical parameters, and controlling the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter.

[0052] In S2 above, the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter are controlled according to the electrical parameters. Specifically, the power coordination controller identifies the current power quality status according to the electrical parameters, including voltage over-limit, harmonic over-limit, three-phase imbalance and transient disturbances.

[0053] If the above power quality conditions do not exist, energy storage charging and discharging control is adopted; if the above power quality conditions exist, active power, reactive power, harmonics and negative sequence components are analyzed, and corresponding voltage compensation commands and / or current compensation commands are generated accordingly. The voltage compensation commands are sent to the UPQC series compensation converter, and the current compensation commands are sent to the UPQC parallel compensation converter.

[0054] It also includes: dynamically adjusting the compensation magnitude of voltage compensation commands and / or current compensation commands based on the state of charge (SOC) value of the energy storage battery module; wherein, when the SOC value is higher than a preset threshold, the system power is allocated in a way that prioritizes meeting the power quality compensation requirements; when the SOC value is lower than a preset threshold, the current compensation depth of the UPQC parallel compensation converter is reduced, and the system control objective is switched to maintain the grid connection point voltage stability as the primary objective.

[0055] Since the principle behind the problem solved by this method is similar to that of the integrated energy storage and power quality system in Embodiment 1 above, the implementation of this method can refer to the implementation of the aforementioned system, and the repeated parts will not be described again.

[0056] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An integrated energy storage and power quality system, characterized in that, include: The system comprises an energy storage battery module, a unified DC bus, a UPQC series compensation converter, a UPQC parallel compensation converter, and a power coordination controller. The DC terminals of the UPQC series compensation converter, the UPQC parallel compensation converter, and the energy storage battery module are all connected to the unified DC bus. The UPQC series compensation converter is connected to the grid side via an isolation transformer. The UPQC parallel compensation converter is connected to the load side. The power coordination controller is communicatively connected to the UPQC series compensation converter, the UPQC parallel compensation converter, and the energy storage battery module, and is used to coordinate and control the charging and discharging of the energy storage battery module, and to control the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter, based on the electrical parameters of the grid side and the load side.

2. The integrated energy storage and power quality system as described in claim 1, characterized in that, It also includes a battery management system; the battery management system is connected between the energy storage battery module and the unified DC bus, and is communicatively connected to the power coordination controller.

3. The integrated energy storage and power quality system as described in claim 1, characterized in that, It also includes a power quality monitoring module; the power quality monitoring module is used to collect electrical parameters of the grid side and the load side in real time and transmit them to the power coordination controller. The power coordination controller identifies the current power quality status based on the electrical parameters, generates corresponding voltage compensation commands and / or current compensation commands, and sends the voltage compensation commands to the UPQC series compensation converter and the current compensation commands to the UPQC parallel compensation converter.

4. The integrated energy storage and power quality system as described in claim 3, characterized in that, The power coordination controller is also used to dynamically adjust the compensation magnitude of the voltage compensation command and / or current compensation command based on the state of charge value of the energy storage battery module; wherein: when the state of charge value is higher than a preset threshold, the system power is allocated in a manner that prioritizes meeting the power quality compensation requirements; when the state of charge value is lower than the preset threshold, the current compensation depth of the UPQC parallel compensation converter is reduced, and the system control objective is switched to maintain the grid connection point voltage stability as the primary objective.

5. The integrated energy storage and power quality system as described in claim 1, characterized in that, The compensation actions of the UPQC series compensated converter include at least one of voltage sag support, overvoltage suppression, voltage flicker mitigation, and three-phase voltage imbalance regulation.

6. The integrated energy storage and power quality system as described in claim 1, characterized in that, The compensation actions of the UPQC parallel compensation converter include at least one of harmonic current filtering, reactive power compensation, three-phase current imbalance regulation, and power factor correction.

7. The integrated energy storage and power quality system as described in claim 1, characterized in that, The UPQC series compensation converter and the UPQC parallel compensation converter together constitute the only power conversion interface between the energy storage battery module and the AC power grid.

8. A control method for an integrated energy storage and power quality system, characterized in that, The system applied to any one of claims 1-7 includes the following steps: S1, acquiring electrical parameters on the grid side and the load side; S2, coordinating and controlling the charging and discharging of the energy storage battery module and the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter according to the electrical parameters through the power coordination controller.

9. The control method for the integrated energy storage and power quality system as described in claim 8, characterized in that, In step S2, the compensation actions of the UPQC series compensation converter and the UPQC parallel compensation converter are controlled according to the electrical parameters. Specifically, the power coordination controller identifies the current power quality status according to the electrical parameters, generates corresponding voltage compensation commands and / or current compensation commands, and sends the voltage compensation commands to the UPQC series compensation converter and the current compensation commands to the UPQC parallel compensation converter.

10. The control method for the integrated energy storage and power quality system as described in claim 9, characterized in that, Also includes: The compensation magnitude of the voltage compensation command and / or current compensation command is dynamically adjusted based on the state of charge value of the energy storage battery module; wherein: when the state of charge value is higher than a preset threshold, the system power is allocated in a manner that prioritizes meeting the power quality compensation requirements; When the state of charge value is lower than a preset threshold, the current compensation depth of the UPQC parallel compensation converter is reduced, and the system control objective is switched to maintain the grid connection point voltage stability.

Images