The energy storage PCS converter is the core equipment of electrochemical energy storage systems, undertaking the key functions of bidirectional energy conversion between energy storage batteries and the power grid, power grid peak shaving and frequency regulation, voltage and frequency support, and new energy consumption. Its grid adaptability directly determines the stable operation capability of energy storage systems under various normal and abnormal grid conditions, serving as a core assessment item for grid connection certification, R&D testing, and mass production inspection of energy storage power stations. The high‑voltage grid simulation power supply is the key device for the grid adaptability test of energy storage PCS converters. It simulates various normal and abnormal grid operating conditions and provides standard compliant AC high‑voltage power supply for PCS converters. Its grid condition simulation capability, output accuracy, dynamic response speed, harmonic superposition capability, and long‑term operational stability directly determine the accuracy, compliance, and safety of PCS grid adaptability test results. At present, the grid connection standards for energy storage PCS require the grid simulation power supply to have an output voltage range of AC 0~480V/690V/1140V and a continuously adjustable frequency range of 40~70Hz. It shall realize full‑condition simulation including voltage sag, swell, interruption, harmonic superposition, three‑phase unbalance, frequency deviation, and voltage flicker, with a dynamic response time ≤5ms and four‑quadrant operation capability to absorb energy fed back by the PCS. Traditional regulated power supplies suffer from weak grid simulation capability, slow dynamic response, inability to output programmable harmonics, and poor adaptability to full‑condition PCS tests, failing to meet the stringent requirements of relevant grid connection standards such as GB/T 36547, GB/T 34120, and IEC 61000‑4. The design shall strictly comply with national and international standards including GB/T 36547 Technical Requirements for Grid‑Connected Inverters of Electrochemical Energy Storage Systems, GB/T 34120 Technical Specification for Electrochemical Energy Storage Systems Connected to Power Grids, GB/T 19964 Technical Requirements for Photovoltaic Power Stations Connected to Power Systems, and the IEC 61000‑4 series Electromagnetic Compatibility — Testing and Measurement Techniques. Meanwhile, it shall match the core requirements of automated full‑condition programmability, bidirectional energy flow, and safety interlock protection for PCS testing. Targeting the key application demands and technical challenges of high‑voltage power supplies for grid adaptability testing of energy storage PCS converters, this methodology establishes a full‑process general technical framework covering full‑condition grid simulation topology design, programmable condition control, fast dynamic response optimization, harmonic superposition algorithms, energy storage test scenario adaptation, and safety protection design. It satisfies the full‑item grid adaptability testing requirements for residential, industrial and commercial, and grid‑scale energy storage PCS converters, providing standardized design criteria for the localization and performance improvement of domestic energy storage testing equipment.
Addressing the core design challenges of full‑condition grid simulation, wide‑range programmable output, fast dynamic response, and bidirectional energy flow in energy storage PCS test scenarios, this methodology adopts a back‑to‑back bidirectional converter main architecture of “front‑stage bidirectional PFC rectification + rear‑stage three‑level NPC inversion + fully digital programmable synchronous control”, combined with grid condition modeling and multi‑variable feedforward compensation algorithms. It fundamentally eliminates the technical bottlenecks of traditional power supplies such as weak grid simulation capability, slow dynamic response, and poor programmability, achieving high‑precision full‑condition grid characteristic simulation and rapid dynamic response in accordance with national and industrial standards, which fully meets the requirements of comprehensive grid adaptability testing for energy storage PCS converters. The design follows five core criteria. First, the topology adopts a back‑to‑back bidirectional four‑quadrant converter structure to realize bidirectional energy flow and full‑condition grid simulation. The front stage applies a three‑phase three‑level Vienna bidirectional PFC rectifier topology to achieve unity power factor rectification and bidirectional energy feedback on the grid side, with a power factor ≥0.99 and total harmonic distortion ≤3%. It rectifies grid AC into stable DC bus voltage to provide steady input for the rear‑stage inverter, and also converts DC power fed back by the PCS into synchronous AC for feedback to the grid, greatly reducing energy consumption during PCS testing. In addition, it achieves electrical isolation between the grid side and the test side to enhance anti‑interference capability and equipment safety. The rear stage adopts a three‑phase three‑level NPC inverter topology. Compared with conventional two‑level inverters, this topology provides more output voltage levels, lower harmonic content, smaller dv/dt, and weaker electromagnetic interference, while reducing voltage stress on power devices and improving reliability under high‑power output, suitable for testing high‑voltage high‑power 690V/1140V energy storage PCS. With SPWM modulation, continuous programmable adjustment of output voltage amplitude, frequency and phase is realized, and specific harmonics can be accurately superimposed to simulate various abnormal grid conditions, covering all grid adaptability test scenarios for PCS. The topology supports four‑quadrant operation, supplying active power to the PCS and absorbing both active and reactive power fed back by grid‑connected PCS, fully adapting to full charge‑discharge test conditions. For high‑power PCS testing, a modular parallel architecture with master‑slave control and fiber synchronization enables parallel operation of multiple power modules with current sharing accuracy better than ±1%, allowing flexible power expansion from tens of kilowatts to tens of megawatts for grid‑scale energy storage PCS tests. Each module features independent control and protection and can automatically exit from parallel operation upon failure without affecting other modules, improving redundancy and reliability of the test system. Second, a full‑condition programmable grid simulation architecture adopts a dual‑core “DSP+FPGA” control framework with an all‑fiber synchronous communication bus to realize high‑precision programmable simulation of full‑condition grid characteristics. The DSP executes core control algorithms, grid condition modeling, communication interaction and logic control, while the FPGA implements PWM modulation, high‑speed sampling, harmonic superposition, and hardware protection logic. The control loop update frequency ≥20kHz and harmonic modulation frequency ≥100kHz significantly increase control bandwidth and response speed while ensuring accuracy and real‑time performance of harmonic superposition. A standardized built‑in grid condition model library fully covers all grid adaptability test conditions specified in GB/T 34120, GB/T 36547 and the IEC 61000‑4 series, categorized into steady‑state models, transient models, and power quality anomaly models. Steady‑state models support continuously adjustable output voltage from 0~120% rated value, frequency from 40~70Hz, and power factor from ‑1~+1 for steady‑state performance testing of PCS. Transient models realize accurate simulation of voltage sag (0~90% voltage drop, duration 10ms~10min), voltage swell (10%~40% rise, duration 10ms~10min), short interruption (0% output, 10ms~5s), voltage gradual change, and phase jump (0~360° sudden shift), with timing accuracy ≤1ms, fully complying with national standards for low‑voltage ride‑through, high‑voltage ride‑through, and phase jump adaptability tests. Power quality anomaly models support superposition of 2nd~50th harmonics and interharmonics, three‑phase unbalance (0~100% unbalance factor), voltage flicker (programmable short‑term flicker value Pst and long‑term flicker value Plt), voltage spikes, and electrical fast transient bursts, covering all power quality adaptability test requirements for PCS. A visual condition editing interface allows users to customize complex timing sequences via drag‑and‑drop and parameter configuration, enabling automatic switching of multi‑stage conditions. All parameters can be saved as templates for repeated use, and actual measured grid disturbance data can be imported to reproduce real abnormal grid scenarios for field condition replication tests of PCS converters. Third, fast dynamic response and output stability optimization criteria address frequent load changes and rapid condition switching in PCS tests by adopting a dual closed‑loop composite control algorithm with load and grid feedforward to achieve extreme dynamic response and steady output. The outer voltage loop uses quasi proportional resonant (QPR) control for zero static error tracking of AC sine waves at the fundamental frequency, while multi‑resonant controllers ensure accurate tracking of specified harmonic components for high‑precision harmonic superposition. The inner current loop employs deadbeat predictive control to predict drive signals for the next control cycle based on sampled current and load models, accelerating current tracking and improving disturbance rejection by more than 80%, with response time ≤1ms. A multi‑variable feedforward compensation algorithm introduces load current feedforward, DC bus voltage feedforward, condition switching feedforward, and grid voltage feedforward. It adjusts drive signals within one control cycle during step load changes, DC bus fluctuations, or grid condition switches, eliminating conventional closed‑loop delay and restricting output voltage fluctuation within ±2% rated value with recovery time ≤5ms during sudden load changes, fully meeting fast switching requirements of PCS charge‑discharge tests. A DC bus voltage regulation algorithm based on front‑stage bidirectional PFC keeps DC bus fluctuation ≤±5% during condition switching and load transients, providing stable input for the rear inverter and further enhancing output stability. An adaptive three‑phase unbalanced load control strategy adopts independent per‑phase closed‑loop regulation, maintaining three‑phase output unbalance ≤1% even under 100% unbalanced loads, suitable for single/three‑phase mixed and unbalanced PCS test scenarios. Fourth, full adaptation criteria for energy storage PCS test scenarios integrate standard built‑in test templates fully complying with GB/T 36547 and GB/T 34120, including steady voltage adaptability, steady frequency adaptability, low‑voltage ride‑through, high‑voltage ride‑through, three‑phase unbalance adaptability, harmonic adaptability, voltage flicker adaptability, phase jump adaptability, anti‑islanding, and active/reactive power regulation capability tests. One‑click automatic testing via upper computer eliminates manual intervention. High‑precision measurement and data recording adopt 24‑bit high‑resolution ADC for synchronous three‑phase voltage and current sampling at ≥100kHz, accurately capturing amplitude, frequency, phase, harmonic content and unbalance factors, while collecting PCS input power, power factor and harmonic current to support comprehensive performance evaluation. Full‑cycle data logging with adjustable sampling intervals from 100μs to 1s supports long‑term durability tests and generates certification‑ready test reports with full data traceability. Multi‑channel synchronous trigger interfaces achieve μs‑level synchronization with battery simulators, power analyzers, data acquisition systems and fault recorders for fully automated coordinated testing of grid adaptability, charge‑discharge performance and protection functions. Communication interfaces compatible with CANopen, Modbus, TCP/IP and IEC 61850 enable coordinated testing with BMS and EMS. Rich fault simulation functions replicate grid short circuits, disconnection, grounding faults, frequency collapse and voltage collapse to verify PCS protection and ride‑through capabilities for functional safety validation. Multi‑unit parallel and multi‑channel independent output support power expansion for high‑power grid‑scale PCS and simultaneous testing of multiple PCS units to improve production line efficiency. Fifth, full‑dimensional safety protection and reliability design criteria address high‑voltage high‑power test risks with a fifteen‑level redundant protection scheme combining hardware and software, including input over/under voltage, input overcurrent, output overvoltage, output overcurrent/short circuit, power device overtemperature, DC bus overvoltage, overload, phase loss, reverse phase, cooling system fault, islanding, safety door interlock, emergency stop, and PCS fault interlock. All hardware protection circuits use independent analog designs with fault response ≤1μs, independent of software control. Dual short‑circuit protection combines fast fuses and electronic current limiting; the electronic loop limits current to safe levels within 1μs during output short circuits, while fuses disconnect the fault within 10ms to prevent device damage and fault escalation. Islanding protection immediately disconnects the front‑stage PFC from the grid and stops output upon detecting grid power loss to avoid islanding hazards. High‑voltage interlock ensures high‑voltage output is enabled only when safety doors are closed, high‑voltage connectors are properly connected and interlock loops are intact. Any interlock trip instantly cuts high‑voltage output and activates active discharge to reduce residual voltage on DC bus and output terminals to safe levels within 100ms, protecting operators. Hardwired emergency stop with dual normally closed contacts cuts main power and blocks all drive signals unconditionally. Dual redundant sampling and protection cross‑validate two independent voltage/current sampling paths; protection triggers immediately if deviation exceeds thresholds, preventing control anomalies and protection failure caused by single‑path sampling errors.
Full‑condition grid simulation and harmonic superposition optimization form the core of this methodology. In response to stringent requirements on simulation accuracy, harmonic capability and dynamic response in PCS grid adaptability tests, the methodology establishes comprehensive optimization guidelines covering grid condition modeling, harmonic superposition algorithms, control loop enhancement, and multi‑unit coordination. In grid condition modeling and programmable control, standardized model libraries strictly follow GB/T 34120, GB/T 36547 and IEC 61000‑4 to ensure compliance and authority of test results. Built‑in low‑voltage ride‑through templates support symmetrical three‑phase, asymmetrical two‑phase and single‑phase voltage drops with adjustable depth, duration and phase angle, switching time ≤1ms and waveform distortion ≤5%, fully meeting national standards. Independent programmable harmonic models allow separate configuration of amplitude and phase for 2nd~50th harmonics with superposition accuracy better than ±5% of set values, supporting interharmonics and subharmonics in accordance with IEC 61000‑4‑7. Voltage flicker models comply with IEC 61000‑4‑15, generating rectangular and triangular voltage fluctuations with adjustable modulation frequency and depth to precisely output specified Pst and Plt values. Programmable timing sequences enable automatic multi‑stage condition switching with configurable duration and cycles to simulate continuous grid variations for durability cycling tests. Import of standard COMTRADE fault records enables direct replication of actual grid fault waveforms for real‑world adaptability verification of PCS converters. In high‑precision harmonic superposition algorithm optimization, multi‑resonant controllers based on repetitive control achieve zero static error tracking for each targeted harmonic by setting infinite open‑loop gain at harmonic frequencies, ensuring accurate superposition. Optimized SVPWM with irregular sampling improves modulation precision and real‑time performance, while carrier phase shifting reduces low‑order harmonic content at the output. Closed‑loop harmonic correction adopts FFT to decompose actual harmonic amplitude and phase, dynamically adjusting reference commands to compensate harmonic attenuation caused by load variation and line impedance, maintaining stable superposition accuracy. Phase synchronization keeps each harmonic aligned with the fundamental and grid voltage with phase accuracy ≤1°, meeting standard requirements for harmonic related tests. In control loop and dynamic response optimization, an FPGA‑based fully digital control architecture achieves sampling and loop update frequencies above 20kHz, reducing control delay to within one cycle compared with pure DSP solutions and greatly improving bandwidth and response speed. Enhanced dual closed‑loop control integrates QPR plus multi‑resonant control in the outer voltage loop for accurate fundamental and harmonic regulation, while deadbeat predictive current control enables fast current tracking and strong disturbance suppression. Load adaptive control identifies impedance characteristics in real time and automatically tunes loop parameters to maintain precise undistorted output under resistive, inductive, capacitive and nonlinear loads. Smooth condition transition algorithms eliminate output shocks and oscillations during mode switching through gradual adjustment of voltage amplitude and frequency, enabling seamless transitions for dynamic PCS condition tests. In multi‑unit coordination and large‑scale expansion, a fiber‑based synchronization bus realizes cascaded global synchronization with inter‑channel trigger accuracy ≤10μs for simultaneous testing of multiple PCS units in large‑scale energy storage power station parallel scenarios. A master‑slave architecture assigns global timing, test management and data aggregation to the master unit, while slave units execute synchronous commands and local sampling via high‑speed fiber communication, ensuring overall control precision and synchronization. Distributed data storage enables local recording in each unit plus real‑time Ethernet upload to the upper test platform, supporting centralized management and traceability for mass production multi‑station testing.
Targeting the core application requirements and technical challenges of high‑voltage power supplies for grid adaptability testing of energy storage PCS converters, this methodology forms a complete technical framework from full‑condition grid simulation topology and programmable condition control to fast dynamic response optimization and full‑dimensional safety protection. It thoroughly solves the key weaknesses of traditional power supplies including weak grid simulation, slow dynamics, low harmonic accuracy and poor programmability. The back‑to‑back bidirectional converter topology realizes efficient bidirectional energy flow and regenerative feedback; fully digital programmable control achieves standard compliant full‑condition grid modeling; composite control plus feedforward compensation delivers dynamic response within 5ms. The methodology fully satisfies comprehensive grid adaptability testing for energy storage PCS converters and can be widely applied in R&D verification, grid certification and production line inspection of residential, industrial‑commercial and grid‑scale PCS products, providing core technical support for domestic substitution and performance upgrading of China’s energy storage testing equipment.