Company Profile

Zhejiang Ximu Electric Co., Ltd. specializes in the R&D, production, sales and integrated services of smart power, intelligent evacuation, PV-storage-direct-flex system, DC power distribution and new power system equipment.

The company focuses on the fields of buildings, industrial parks, scenic spots, transportation, industry and new energy, providing safe, efficient, low-carbon and intelligent one-stop overall electrical solutions.

Supported by technological innovation from Southeast University and Nanjing University of Aeronautics and Astronautics, the core team has years of in-depth experience in power electronics and power systems, with mature capabilities in transforming scientific research achievements into industrialized applications.

Based on advanced manufacturing and power electronics technologies, Ximu Electric deeply integrates smart power and PV-storage-direct-flex technologies to facilitate the implementation of the dual-carbon strategy, and strives to become a leading domestic service provider of intelligent electrical solutions.

Project Overview

2.1 Project Background

Aiming at power supply pain points of two transformer districts and combining operating parameters of each 400kVA transformer, this project deploys energy storage systems to solve overvoltage caused by low district load or excessive photovoltaic power generation, as well as undervoltage during peak load periods. Meanwhile, it meets the daily operation requirement of two charge-discharge cycles per day, guarantees power supply stability, improves power quality, reduces grid operation and maintenance pressure, adapts to district operation demands after distributed photovoltaic integration, and realizes coordinated operation of source, grid, load and storage.

2.2 Core Requirements

Peak Shaving Requirement: Suppress grid peak power by absorbing redundant electric energy when district voltage exceeds upper limit, avoid voltage out-of-limit (exceeding safety threshold) and risk of equipment damage.

Valley Filling Requirement: Solve undervoltage at night; release electric energy to the grid during off-peak hours to boost line voltage, ensure normal operation of high-power appliances such as air conditioners and refrigerators, and improve power consumption experience for users.

Operation Mode: Realize two charging and two discharging cycles every day, fully utilize the benefit of peak-valley electricity price difference, balance voltage regulation effect and economy, and adapt to high-rate charge-discharge demands of batteries.

Energy Storage Configuration: Transformer District 1 (District 1 for short): 60kW/120kWh; Transformer District 2 (District 2 for short): 125kW/261kWh. Both are deployed on the low-voltage side of corresponding 400kVA transformers to realize on-site regulation.

2.3 Applicable Standards

This scheme strictly complies with Technical Conditions for Control Devices of Distributed Energy Storage Systems Connected to Distribution Transformer Districts (T/CES 299-2024), Technical Guidelines for Grid-Connection of Distributed Electrochemical Energy Storage on Transformer District Side (T/CI 1120-2025), Guidelines for Power System Security and Stability and relevant grid-connected specifications for distribution energy storage issued by local power grid companies, ensuring safe grid connection and compliant operation. It also meets national mandatory inspection standards for lithium iron phosphate batteries (GB/T 36276).

Overall System Design

3.1 Design Principles

Safety First: Adopt energy storage equipment with high safety level, equipped with complete fire protection, lightning protection and overload protection, build a multi-level electrical protection system of "Cell – Module – String – System" to eliminate potential safety hazards.

Precise Demand Matching: Energy storage power and capacity match district load characteristics and 400kVA transformer capacity to guarantee peak shaving and valley filling effects, strictly satisfy two charge-discharge cycle requirements per day, and take battery cycle life into consideration.

Intelligent Control: Rely on EMS Energy Management System to realize automatic charge-discharge, voltage regulation, fault early warning and remote monitoring, reduce manual intervention and improve operation efficiency.

Reasonable Economy: Optimize equipment selection and operation strategy, prioritize highly integrated and long-life products to lower initial investment and later operation & maintenance costs, and increase revenue via arbitrage of peak-valley electricity prices.

Strong Expandability: Modular system design supports multi-unit parallel connection and cluster management, reserves expansion interfaces for future demands of load growth and grid upgrading.

3.2 System Architecture

The energy storage system of each transformer district adopts an integrated architecture of "Energy Storage Battery Pack + BMS Battery Management System + PCS Power Conversion System + EMS Energy Management System + Auxiliary Protection System", deployed on the 0.4kV low-voltage side of transformers and independently connected to district power grid. It forms a closed-loop regulation system together with transformers and loads, realizing internal energy self-regulation without scheduling from the main grid, equivalent to a "giant intelligent power bank plus voltage stabilizer" for the transformer district.

Core System Logic: EMS collects real-time parameters including district voltage, current, load power and grid frequency, issues instructions to control PCS switching between charging and discharging according to preset strategies. BMS monitors battery status in real time to ensure safe and stable battery operation. The auxiliary protection system deals with abnormalities such as overcurrent, overvoltage and short circuit to guarantee system safety throughout its whole lifecycle.

3.3 Overall Topology

Grid (10kV) → 400kVA Transformer → Low-Voltage Distribution Cabinet → Energy Storage System (PCS + Battery Pack + BMS + EMS) → District Load; The EMS communicates with PCS, BMS, low-voltage distribution cabinet and transformer measurement & control devices respectively, acquires real-time operating data and issues control instructions to realize closed-loop control of "Collection – Analysis – Decision – Execution". Meanwhile, it supports docking with grid dispatching platform and cloud operation & maintenance platform to implement remote monitoring and strategy issuing.

4.2 Configuration of District 2 (125kW/261kWh)

4.3 Equipment Selection Explanation

1. Battery Selection: Lithium iron phosphate battery is preferred, featuring high safety performance and long cycle life (≥8000 cycles, SOH≥70%), suitable for daily two high-frequency charge-discharge cycles with slow capacity attenuation, meeting long-term operation requirements of district energy storage. It also passes national mandatory inspection standards to ensure operation safety.

2. PCS Selection: Bidirectional high-efficiency converter with response time ≤ 80ms to meet rapid voltage regulation demands, efficiency ≥ 98% to reduce energy loss, supports grid-connected/off-grid switching and can act as backup power supply for critical loads during grid abnormalities, with grid support capability to improve power quality.

3. EMS Selection: Industrial-grade EMS system with high compatibility and reliability, supporting multi-device communication and data acquisition, flexible strategy configuration to adjust charge-discharge strategy dynamically according to district load and voltage fluctuation, as well as remote monitoring and maintenance to cut labor cost.

4. Temperature Control System: Air cooling is adopted for District 1 according to capacity demand, while high-efficiency liquid cooling system is applied for District 2 to control cell temperature difference within 5℃, avoid overheating caused by frequent charge-discharge, extend battery life and adapt to various outdoor ambient temperatures.

Installation & Deployment Scheme

5.1 Installation Location Selection

The energy storage cabinets of both districts are installed in open outdoor areas beside corresponding 400kVA transformers, complying with the following requirements: Distance to transformer low-voltage distribution cabinet ≤ 10m to reduce line loss, facilitate cable connection and minimize voltage drop impact.

The site shall be flat and solid with bearing capacity ≥ 2.5t/㎡ (matching cabinet weight), no water accumulation, unobstructed, well ventilated and away from direct sunlight.

Keep away from flammable & explosive materials and residential areas (distance ≥ 5m) in accordance with fire codes; reserve maintenance space ≥ 1.5m around cabinets for equipment overhaul.

5.2 Electrical Connection

1. Connection between energy storage system and transformer low-voltage side: Connect PCS output terminal of energy storage cabinet to low-voltage distribution cabinet via copper cables, cable specification selected by power rating (District 1: 35mm²; District 2: 70mm²). Adopt conduit laying with complete insulation protection to prevent short circuit and electric leakage.

2. Control wiring: EMS connects with PCS, BMS, low-voltage distribution cabinet and transformer measurement & control devices via RS485/Ethernet ports for data interaction and instruction issuing; it can also access grid dispatching system to upload operating data and receive dispatching instructions if required.

3. Earthing System: Reliably earth energy storage cabinet, PCS, battery pack and low-voltage distribution cabinet to form a unified earthing network with earthing resistance ≤ 4Ω, preventing live equipment enclosure and protecting personal & equipment safety.

5.3 Installation Procedure

EMS Control Logic (Core Part)

As the core of district energy storage system, EMS Energy Management System is responsible for overall equipment operation coordination and charge-discharge strategy formulation to realize voltage regulation, strictly satisfying three core demands of peak shaving, valley filling and two charge-discharge cycles daily. It adopts closed-loop mode of "Real-time Monitoring – Intelligent Analysis – Instruction Issuing – Feedback Adjustment", dynamically optimizes control strategy combined with district load characteristics, voltage fluctuation and battery status, and supports both cloud remote regulation and local autonomous operation. Detailed logic is as follows:

3. Upon grid faults (power outage, frequency abnormality), PCS automatically switches to stop/standby mode, returns to grid-connected mode after grid recovery, adjusts charge-discharge strategy to complete remaining two charge-discharge cycles.

6.4 Remote Monitoring & Operation & Maintenance Logic

• Real-time Monitoring: EMS communicates with cloud platform and grid dispatching center via 4G/Ethernet, uploads real-time system operating data (voltage, current, SOC, equipment status, etc.), supporting remote viewing via PC and mobile terminals.

• Fault Early Warning & Handling: Trigger local audible & visual alarm plus cloud alarm once equipment abnormalities (battery over-temperature, PCS fault, abnormal voltage, etc.) occur; record fault information automatically, take emergency measures (pause charge-discharge, cut off circuit, etc.) and notify maintenance personnel for timely disposal.

• Remote Regulation: Maintenance staff can remotely adjust charge-discharge time, power, voltage threshold and other parameters via cloud platform to adapt to changing district operating conditions without on-site operation.

• Data Statistics & Analysis: EMS automatically counts daily charge-discharge times, electricity quantity, voltage regulation effect and battery degradation data, generates daily, weekly and monthly reports to support maintenance decision-making and strategy optimization.

System Commissioning & Trial Operation

7.1 Commissioning Contents

• Individual Equipment Commissioning: Test BMS, PCS, EMS, temperature control system and fire protection system separately, check operating status, parameter setting and protection functions to ensure normal equipment operation.

• Joint Commissioning Test: Operate all equipment coordinately, simulate scenarios of two charge-discharge cycles, peak shaving and valley filling, verify accuracy and response speed of EMS control logic, inspect voltage regulation effect and optimize control parameters.

• Grid-Connection Test: Connect energy storage system to power grid, test grid-connection stability and power quality (voltage, frequency, harmonic), comply with grid connection specifications without reverse power delivery or voltage out-of-limit issues.

• Protection Function Test: Simulate abnormalities such as overcharge, over-discharge, over-temperature, short circuit and lightning strike, verify response speed and effectiveness of protection system to guarantee safety of equipment and power grid.

7.2 Trial Operation Scheme

Enter trial operation phase for 7 days after qualified commissioning with specific requirements as follows:

• During trial operation, the system runs according to preset two charge-discharge strategy and peak-valley regulation logic; EMS monitors operating data in real time and records voltage variation, charge-discharge status and equipment conditions.

• Check equipment operation daily, eliminate hidden faults and record trial operation data including charge-discharge times, electricity quantity, voltage regulation range and battery SOC variation.

• Stop operation for timely troubleshooting and parameter optimization if abnormal voltage or equipment faults occur during trial operation to guarantee stable system performance.

• Sort out trial operation data after completion, analyze overall system performance, further optimize and adjust if requirements are not met before formal commercial operation.

Operation & Maintenance Scheme

8.1 Fault Handling

Establish emergency fault handling mechanism and clear workflow to ensure timely troubleshooting and minimize downtime:

• Fault Reporting: Once maintenance personnel receive local or cloud alarms, record fault type, occurrence time and phenomenon immediately and report to relevant person in charge.

• Fault Troubleshooting: Analyze root causes (battery abnormality, PCS failure, line fault, etc.) according to fault information and formulate disposal plan.

• Fault Disposal: Arrange professional technicians for troubleshooting with complete safety protection measures to avoid secondary faults; test equipment operation after repair to confirm fault elimination.

• Fault Filing: Archive whole process, root cause and result of disposal, analyze fault pattern, optimize maintenance scheme and prevent recurrence of similar failures.

8.2 Battery Maintenance