Quick Switchgear + PCS Seamless Switching Solution (<20ms)

Document Date: 2026-09-07 Issuing Department: Hoenergy — Overseas Business Division, Technology Center Prepared by: Alvin

§0 30-Second Briefing (Executive Summary)

Q. Core Customer Question: How can an energy storage system keep the load powered during a grid outage, and how fast can the switching time be?

🔴 A. Key Conclusions

B. Three Red Lines at a Glance

See Appendix A for the complete list of red lines R1–R10.

§1 Product Portfolio (Hoenergy D-Cube + EVALUE EQS)

1.1 Product Portfolio Overview

1.2 Enjiu EQS Series (6 Models, Full Current Range)

⚠️ Paired with a 125 kW PCS (AC400 V), the switching time is ≤20 ms; paired with a 215 kW PCS (AC800 V), the switching time is ≤30 ms.

EQS Technical Specifications: EQS Product Datasheet

1.3 EQS Product Dimensions and Installation

1.3.1 Product Dimensions

1.3.2 Installation Method

✅ Correct installation method: Mount vertically on the wall, perpendicular to the ground

❌ Incorrect installation method: Installed parallel to the ground

§2 EQS Selection (by 125 kW PCS unit count × N)

2.1 Selection General Principle: Dual-Condition Determines

Core formula:

EQS apparent capacity ≥ PCS maximum charging power + load usage power (must be satisfied under any operating condition)

Why the dual condition is the determining condition:

1. Charging current path: Grid → EQS → PCS → Battery (passes through the EQS)
2. Load current path: Grid → EQS → Load (passes through the EQS)
3. The two currents algebraically superimpose at the EQS (same direction)
4. When the charging period (energy storage replenishment during off-peak electricity price periods) overlaps with a high-load period → EQS flow reaches its peak

Charging power assumption (typical operating conditions):

2.2 Load Requirements (EnJoy PCS Off-Grid Load Capacity)

The three scenarios that VSG truly improves are:

1. Motor starting — Virtual inertia J simulates rotor energy storage, capable of absorbing 6-8 times the inrush current without causing frequency collapse (in VF mode, the inrush current directly causes frequency drop);
2. Transformer magnetizing inrush current — Virtual damping D suppresses transient oscillations;
3. Multi-machine parallel power sharing — More stable based on virtual impedance.

Loads that cannot be applied or require special evaluation (same restrictions as VF mode):

1. Single-phase high-power equipment (>30% of total power) requires a DyN11 isolation transformer;
2. Direct starting of large motors (>10 kW) requires soft starting or star-delta step-down;
3. Non-linear loads (inverters, rectifiers, THD > 8%) require active power filter APF;
4. Impact loads (spot welders, arc furnaces) require PCS capacity amplification by 1.5-2 times;
5. Oversized capacitor compensation cabinet (>30% PCS capacity) may cause self-excited oscillation;
6. Parallel operation with diesel generators/PV requires synchronous verification and coordinated control.

2.2 Single-Condition Selection Table (Load Only, Battery Not Charging)

Assumptions:

• cosφ = 0.8 (typical for industrial and commercial loads before compensation; typically 0.90–0.98 after compensation)
• In single-condition operation, the PCS only discharges, with sufficient battery state of charge
• Maximum load under single condition P_load = N × 100 kW (80% of PCS capacity, reserving a 20% PCS capacity margin, an engineering-conservative assumption)
• The full-load rating per unit (125 kW/unit) is covered in §2.9 Benchmark Case (extreme condition)

2.3 Dual-Mode Selection Table (Charging + Load Simultaneously, Most Conservative)

Assumptions (full-power charging, matched to PCS rating):

• Single PCS charging power = 125 kW (full power, same as PCS discharging power)
• Total charging power = N × 125 kW
• Maximum single-mode load P_load = N × 100 kW (80% of PCS capacity, consistent with the engineering convention in §2.2)
• cosφ default 0.8 (typical commercial/industrial)

Source of the full-power charging assumption: The EMS of an energy storage project generally does not limit the charging power (charging periods have low electricity prices, encouraging more charging). The conservative assumption uses full power of 125 kW per unit, forming a contrast with the power-limiting scheme (A) in §6.5.

> User full-load convention (P_load = N × 125 kW) is shown in the benchmark case in §6.9 (1250+1250=2500 kW → EQS-4000R, red line R7), which is more conservative than this table.

⚠️ Critical Warning: Under the full-power charging assumption, more than 4 PCS units approach the upper limit of EQS-2000R, and more than 6 units require upsizing to EQS-2600R/4000R.

2.4 Single-Condition vs Dual-Condition Sizing Comparison (Key Insights)

Key Insights:

• Dual-condition requires a higher-tier EQS than single-condition, with an upgrade magnitude of 1–2 tiers;
• N ≤ 3 units: The difference between single and dual conditions is small; EQS-500/750 can both cover the requirement;
• N = 4–6 units: Dual-condition goes up 1 tier; EQS-2000R is the maximum capacity that can be covered within the current specification limit;
• N ≥ 7 units: Dual-condition requires EQS-2600R/4000R.

2.5 Engineering Trade-Off Solutions (Dual-Condition Coverage with N ≥ 7 PCS Units)

Option A Detailed Calculation (Limit Charging Power ≤ 50 kW per unit):

Option B Off-Peak Charging (Recommended):

• Off-peak periods: Low electricity price → Charging periods
• Peak periods: High electricity price → Discharge to support load + no charging

With off-peak charging, charging and load periods are naturally staggered, and the dual-condition scenario becomes a single-condition coverage. This is the most commonly used approach for commercial and industrial energy storage.

Option C Expand EQS Selection:

Exceed the project specification upper limit and expand to EQS-2600R (2600 A) or EQS-4000R (4000 A).

• EQS-2600R 400V capacity: 1800 kVA
• EQS-4000R 400V capacity: 2770 kVA
• Suitable for 10 PCS units at full-power charging scenario

2.6 AC 800V High-Voltage Platform Selection

• If the customer adopts an 800V platform (paired with ENJOY 215 kW PCS), the single-condition EQS capacity is doubled (at the same current level), and the switching time is reduced from ≤20 ms to ≤30 ms.

Pattern: 1-2 → EQS-500 | 3-4 → EQS-750 | 5-8 → EQS-1300 | 9-10 → EQS-2000

2.7 Selection Decision Tree

Typical Selection Result Examples:

2.8 Summary of Core Selection Formulas

EQS Apparent Capacity (kVA) ≥ [PCS Charging Power (kW) + Load Power (kW)] / cosφ

S_EQS ≥ (N × P_charge + P_load) / cosφ

Where:
  S_EQS    EQS apparent capacity (kVA)
  N        Number of PCS units
  P_charge Single PCS charging power (kW); equals 0 in single-condition operation
  P_load   Load power (kW)
  cosφ     Power factor (typically 0.90-0.98 after commercial/industrial compensation)

Red Line R6 (Selection Determined by Dual-Condition Operation):

Red Line R7:

10 PCS units charging at full power + 1250 kW full load simultaneously → total power 2500 kW → EQS-4000R (2770 kVA) must be selected, and cosφ ≥ 0.91.

3 Product Portfolio Topology Diagram

3.1 EQS Electrical Wiring Diagram

3.2 S-Series Integrated Energy Storage Cabinet (PCS + Battery Integrated)

• The detailed configuration table is as follows:

3.3 A-Series PCS Integrated Cabinet + 261D Battery Cabinet

The A-Series is an outdoor PCS integrated cabinet launched by HOENERGY, designed to work in conjunction with the D-Cube-261D battery cabinet (physically separate from A, connected via DC bus). The A-Series PCS is also based on the Eneri 125 kW module (sharing the same PCS hardware platform as the S-Series), with verified compatibility against Eneri EQS switching.

A-Series vs S-Series Selection Comparison:

A-Series Integration Example (2 MWh typical configuration):

• D-Cube-A500 (500 kW PCS) × 2 + D-Cube-261D × 8 = 1000 kW PCS + 2.088 MWh
• Connect to EQS-2000R (13385 kVA) or EQS-4000R (2770 kVA)
• For detailed A-Series solutions, please contact HOENERGY technical staff

D-Cube to EQS Interface:

D-Cube AC Output (U/V/W/N2)  ──►  EQS Load-side Terminal
D-Cube DI/DO (VSG Switching) ──►  EQS Control Terminal DO4+/DO4-, DI3+/DI3-
D-Cube VSG Algorithm Enable  ──►  0x5066 / 0x02FF Pre-configured

§4 EQS Internal Structure + ≤20 ms Switching Principle

4.1 EQS Static Switch Core Components

The core of the EQS is a bidirectional thyristor (SCR) anti-parallel static switch, where each pole (A/B/C or plus N) consists of two SCRs connected in anti-parallel to form a bidirectional conduction unit. This is the fundamental reason it can achieve a switching time of ≤20 ms.

4.2 Key Question: Is EQS Pure Solid-State or a Solid-State + Mechanical Hybrid?

Q. Is the EQS a pure solid-state switch (SCR only) or a solid-state + mechanical hybrid?

🔴 A. Solid-state + mechanical hybrid (Hybrid Static Switch) — this is the key design that enables the EQS's 99.97% full-load efficiency:

4.3 ≤20 ms Switching Sequence

Grid-tied → Off-grid (Grid Power Loss):

t=0 ms      Grid fault
t<5 ms      PCS detects bypass voltage 0x0AAF: 0→2 (transient)
t=5-10 ms   EQS control board judges: grid power loss → triggers SCR pre-turn-on preparation
t=10-15 ms  EQS mechanical bypass opens (contact separation)
            + SCR takes over conduction (natural commutation, switched at current zero-crossing)
t=15-20 ms  Mechanical bypass fully open, load current entirely flows through SCR
            + PCS switches to off-grid VSG mode (0x5066=1, 0x02FF=1)
t≤20 ms     Switching complete, load continuously powered by PCS VSG
            + 0x0219 STS control command: 1→0
            + 0x0F3A A3 board DI3 feedback external switch opened

Off-grid → Grid-tied (Grid Recovery):

t=0 s       Grid recovery (0x0AAF: 1→2→0)
t=0 s       PCS enters auxiliary secondary frequency regulation phase
            - EMS reads 0x018C/0x018D to calculate P_tot/Q_tot
            - Sets P_tot/n down to 0x500E (Pset), step ≤10%, interval ≥100 ms
t=90-180 s  Frequency/voltage aligned with grid reference
t=closing instant  EQS mechanical bypass closes (at current zero-crossing)
            + 0x0219 STS control command: 0→1
            + 0x0F3A DI3 feedback external switch closed
t=after closing    SCR naturally turns off, steady-state path resumes mechanical bypass conduction
            + PCS switches to grid-tied VSG mode (0x5066=0)

4.4 Zero-Current Switching Principle

The key for EQS to achieve ≤20 ms is Natural Commutation:

Q. What is natural commutation? Why must switching occur at zero current?

🔴 A. Natural commutation = leveraging the characteristic that the AC current itself crosses zero every 10 ms (50 Hz), completing the SCR channel switching at the instant of current zero-crossing.

• SCR is a semi-controlled device; once it is turned on, it must wait for the current to cross zero before it can be turned off (it cannot be forcibly turned off);
• At 50 Hz mains frequency, the current crosses zero once every 10 ms, so a zero-crossing point is guaranteed within at most 10 ms;
• EQS switches at the current zero-crossing point → zero-current switching, with no arc, no inrush, and no voltage spike;
• This is why the EQS can achieve a lifetime of 1,000,000 cycles (pure mechanical switches suffer contact erosion from arcing, while pure solid-state SCRs incur large continuous conduction losses).

§5 EQS Lifetime Curve + Reliability Data

5.1 EQS Lifetime Algorithm (Hard Selection Criterion for Projects)

EQS Lifetime Selection Formula:

EQS Design Lifetime ≥ Project Lifetime × Annual Switching Cycles × Safety Factor

Where:
- Project Lifetime = 15 years (industrial and commercial standard)
- Annual Switching Cycles = Number of grid anomalies/year × Safety Margin (2-3x)
- Safety Factor = 1.5 (conservative)

Typical Project Lifetime Calculation Examples:

5.2 Source of the 1,000,000-cycle lifespan (ENJOY in-house test)

The EQS 1,000,000-cycle lifespan comes from in-house testing at the ENJOY factory. Key data:

Key interpretation: 1,000,000 cycles refers to the mechanical life (excluding contact wear); the electrical life (including contact wear) is ≥100,000 cycles.
The EQS standard model is factory-rated at 100,000 cycles, while the long-life model is rated at 1,000,000 cycles.

5.4 Selection Recommendations (by Project Type)

§6 Three Core VSG Mechanisms + Coordination with EQS

6.1 Three Core Mechanisms of VSG

6.2 EQS Switching and VSG Three-Mechanism Coordination Timing

                 EQS Mechanical Action        VSG Algorithm Response
                 ─────────────                ────────────
t=0 ms           Grid fault                    PCS detects 0x0AAF=2 (transient)
                                                  ↓
t=0-5 ms         EQS triggers SCR preparation PCS J (virtual inertia) starts
                                                  Releases "virtual rotor kinetic energy"
                                                  Suppresses frequency drop RoCoF
                                                  ↓
t=5-15 ms        EQS mechanical bypass opens   PCS D (virtual damping) starts
                 SCR takes over conduction      Negative feedback suppresses transient oscillation
                                                  ↓
t=15-20 ms      EQS fully opens               PCS Kf (primary frequency regulation) starts
                 Load 100% via SCR              P-f droop, steady-state recovery
                                                  ↓
t≤20 ms          Switching complete            PCS already in steady-state operation
                                                  0x5066=1, 0x02FF=1
                                                  0x500E Pset dispatch command
                                                  ↓
t>20 ms          Steady-state mechanical bypass open VSG continues grid-forming
                 SCR off                        Waits for 0x0AAF=0 (grid recovery)

6.3 Grid-Side Fault — 1.5× Rated Power / 200 ms Grid-Forming Support

Q. Why can the VSG provide 1.5× rated power for 200 ms?

🔴 A. Two layers of reasons:

Application Value:

• In mainstream 0.4 kV commercial and industrial scenarios, instantaneous grid faults (lightning strikes, equipment short circuits) occur approximately 5-10 times per year;
• The VSG's 1.5× support capability enables the PCS to actively inject reactive power during faults, supporting grid-side voltage recovery;
• This is something a pure PQ-controlled PCS cannot achieve — PQ mode merely follows commands and does not actively support the grid.

7 Detailed Benchmark Case Study: Dual-Condition Selection for 10 PCS Units

Q. Customer Question: I need 10 PCS units of 125 kW each (10 × 125 = 1250 kW total PCS power). The load is also 1250 kW (full load), and charging and the load occur simultaneously. Which EQS should I select?

7.1 Charging + Load Power Stacking

Known:

• Number of PCS units N = 10
• Total PCS power = 10 × 125 = 1250 kW
• Total load power = 1250 kW (full load, no margin)
• Charging and load occur simultaneously (time-of-use tariff-free scenario or customer requires 0 switching)
• Total charging power = 10 × 125 = 1250 kW

Calculation (Red Line R6):

7.2 Candidate EQS Model Comparison (10 PCS Units at Dual-Mode Full Power)

Key Conclusion (Red Line R7): 10 PCS units at full-power charging + 1250 kW full load simultaneously → EQS-4000R (2770 kVA) is the only viable model, but with hard engineering constraints:

• cosφ < 0.91 → EQS-4000R overloads (red line triggered; must derate or upsize)
• cosφ ≥ 0.91 → EQS-4000R safe (typically achievable at 0.92-0.98 after industrial SVG/capacitor compensation)
• cosφ ≥ 0.95 → EQS-4000R with 5% margin (ideal operating condition)

7.3 Four Engineering Compromise Path Options (Sorted by Priority)

Recommended Solutions:

§8 EQS Wiring and Signal Definition

7.1 Power Terminals

Note: In the source table, the third load-side phase is labeled "W" with the description "连接 PCS 交流输出 L4 相" (L4 phase). The discrepancy between W and L4 is preserved as in the original.

Translation Notes: - 功率端子 → Power Terminals - 端子类型 → Terminal Type - 丝印 → Silkscreen - 功能 → Function - 备注 → Remarks - 电网侧 → Grid Side - 负载侧 → Load Side - 电网输入 L1 相 → Grid input L1 phase (L1, L2, L3 preserved as technical labels) - 电网输入 N 线 → Grid input N line - EQS-2000R 为 3P 无 N1 → EQS-2000R is 3P without N1 - 红线 R2 → red cable R2 - 连接 PCS 交流输出 L1 相 → Connects to PCS AC output L1 phase - 连接 PCS 交流输出 N 线 → Connects to PCS AC output N line

All Chinese characters have been translated to English. Technical identifiers (EQS-2000R, PCS, R, S, T, U, V, W, N1, N2, L1, L2, L4, R2, 3P) are preserved in their original Latin/numeric form.

7.2 Control Terminals (Core: DIO Digital I/O)

7.3 Control Power Input

⚠️ Red Line R9: The EQS control power 220 VAC must be supplied independently and must not be drawn from the PCS DC bus (to avoid power loss during switching transients).

7.4 EQS-D-Cube Signal Flow Diagram

7.5 Factory Pre-Integration Interfaces (D-Cube ↔ EQS)

§8 Four Working Modes

8.1 Mode Overview

§9 FAQ 与待澄清问题

9.1 FAQ (sorted by inquiry frequency)

Q1. Is the switchover time ≤20 ms real?

🔴 A. EQS "paired with a 125 kW (IP20) PCS ≤20 ms" requires the PCS to be in VSG mode and the DO4/DI3 wiring to be correct.

Q2. After switching to off-grid, how long can the PCS keep running?

🔴 A. Determined by the energy storage capacity. A D-Cube-S125 (125 kWh) running at full load of 125 kW can sustain for 1 hour; a D-Cube-S261 (261 kWh) can sustain for 2 hours at full load; the A series can last up to 8 hours. When SOC falls below 20%, it is recommended to switch to diesel generator or reduce the load.

Q3. Why is the VSG paralleling upper limit 10 units instead of 12?

🔴 A. The VSG algorithm itself supports 12 units, but it is currently limited to 10 units for three reasons:

1. SOC balancing stability: 10 units is the upper limit based on engineering experience;
2. EQS single-unit current density: 10 units × 125 kW = 1.25 MW, which keeps the current density of the EQS-2000R (2000 A) manageable;
3. Future expansion: Phase II of the project can be expanded to 12 units (the theoretical VSG upper limit) without replacing the EQS.

Q4. How is SOC consistency ensured when multiple PCS units are paralleled?

🔴 A. The EMS issues secondary frequency regulation commands via 0x500E/0x500F to allocate power proportionally to SOC. Hard constraint: the power spread among PCS units must be ≤ (total load / number of PCS units) × 20%.

Q5. The EQS-2000R is 3P without N1. Can it be used in TN-C/TN-S systems?

🔴 A. This needs special confirmation. The 3P model has no N1 terminal. If the load in a TN-C/TN-S system requires an N line, a 4P model (EQS-500/750/1300) must be selected, or an external neutral-point treatment must be used.

Appendix A Key Red Lines

A.1 Design Red Lines (Violation will render the solution invalid)

Red Line Numbering Convention: R1-R5 = General engineering constraints (§0.2 cheat sheet); R6-R10 = This project's §6 selection hard constraints (directly drive the §6.x tables); R11-R12 = VSG parameter boundaries (verified during commissioning).