Medium-Voltage Direct-Connect Ultra-Fast Charging Station

Zhejiang Rockwell Energy Technology Co., Ltd.

An SST-Based Solution for Next-Generation EV Charging

1. Industry Background and Pain Points

1.1 Industry Background

With more than 30 million EVs on the road, users now expect charging to feel like refuelling. That demand has driven the shift to ultra-fast charging (350 kW+, 800 V platform). But the conventional "transformer + charger" station architecture hits a systematic wall in power density, efficiency and utilisation of the grid connection.

1.2 Four Pain Points of Traditional Charging Stations

Pain point	Description	Physical root cause
Slow charging	30–60 minutes for a conventional fast charge	Power limited
Low efficiency	Whole-station efficiency of ~90%	Transformer + AC/DC multi-stage losses
Grid impact	Concentrated charging shocks the grid	No energy-storage buffer
Poor grid utilisation	Fixed transformer capacity	No peak-shaving capability

1.3 Traditional vs. SST Direct Connection — the Physical Difference

Traditional charging-station chain

Step	Equipment	Loss	In plain terms
①	10 kV → 0.4 kV transformer	1%–2%	Steps the voltage down for supply
②	AC/DC charging module	3%–5%	Converts AC to DC for charging

Total loss: ~5%–7%, whole-station efficiency of ~90%–93%.

SST direct-connect charging-station chain

Step	Equipment	Loss	In plain terms
①	SST solid-state transformer	1%–2%	Directly connected at 10 kV with integrated rectification, in one step
②	Direct DC busbar supply	Negligible	Multiple guns share one DC bus

Total loss: ~2%–5%, whole-station efficiency of 94.5%–97.5%.

Physical root cause: SST medium-voltage direct connection removes the transformer, cutting charging-chain losses by 3–5 percentage points; the shared DC busbar lets multiple charging guns share power, improving utilisation.

Medium-Voltage Direct-Connect Ultra-Fast Charging Station

2. Solution Overview and Value Proposition

2.1 Solution Definition (BLUF)

The SST direct-connect ultra-fast hybrid charging station delivers:

MW-class extreme charging (100 km of range in 1 minute)
Whole-station efficiency of 94.5%–97.5% (+3–5%)
Grid utilisation of 83% → 120%
World-first proven installation (CNPC Kunshan station)

2.2 Core Value Proposition

Value dimension	Metric	Description
Power per gun	MW-class extreme charging	100 km of range in 1 minute
Whole-station efficiency	94.5%–97.5%	+3–5% vs. traditional
Grid utilisation	83% → 120%	Peak-shaving with coupled energy storage
Charging terminals	Ultra-fast + liquid-cooled	Mixed multi-gun dispatch
Delivery time	1 day	Proven at Kunshan

3. System Architecture

3.1 System Topology (Layer by Layer)

① Medium-voltage connection: 10 kV incoming — with incoming protection and metering
② SST power core: 10 kV AC → multi-port DC busbar
③ Charging terminals: ultra-fast terminals (MW-class extreme charging, 100 km in 1 minute), liquid-cooled ultra-fast terminals (sustained high power), and an energy-storage coupling port (peak shaving)
④ Charging management: charger cluster control + EMS

Layer	Composition	Power flow	Design rationale
① Medium-voltage connection	10 kV incoming	Grid → SST	Medium-voltage direct connection
② SST core	DC busbar	10 kV → Multi-port DC	One busbar, many guns, shared power
③ Charging terminals	Ultra-fast + liquid-cooled + storage	DC → Vehicle	Mixed multi-gun dispatch
④ Management	Cluster control + EMS	Information flow	Power-allocation optimisation

3.2 How the Shared DC Busbar Works

In a traditional station, each charger has its own AC/DC stage and the powers are not shared. In the SST solution, all charging terminals share a single DC busbar, and the total power is allocated on demand — this is the physical basis of the "120% grid utilisation".

Medium-Voltage Direct-Connect Ultra-Fast Charging Station

4. Core Equipment and Technical Parameters

Parameter	Value	Physical significance
Power per gun	MW-class extreme charging	100 km of range in 1 minute
Whole-station efficiency	94.5%–97.5%	+3–5% vs. traditional
Grid utilisation	83% → 120%	Peak-shaving with storage
Charging terminals	Ultra-fast + liquid-cooled	Mixed multi-gun
Delivery time	1 day	Proven at Kunshan

5. Technical Highlights and Physical Principles

5.1 Highlight 1: MW-Class Extreme Charging

Physical principle: the SST medium-voltage direct connection provides an 800 V / 1000 V DC busbar, so the power per gun can reach MW class, breaking through the ceiling of the traditional 400 V platform.
Quantified benefit: 100 km of range in 1 minute — an experience on par with refuelling.

Medium-Voltage Direct-Connect Ultra-Fast Charging Station

5.2 Highlight 2: 120% Grid Utilisation

Physical principle: with a coupled energy-storage port, the station charges storage at off-peak times and discharges at peak times; combined with PV, transformer capacity utilisation can exceed 100%.
Quantified benefit: with the same transformer capacity, more vehicles can be served, improving ROI.

5.3 Highlight 3: One-Day Delivery

Physical principle: modular factory pre-fabrication means the station is lifted into place and ready to use on site.
Quantified benefit: the world-first Kunshan station was delivered in 1 day.

6. Economic Comparison with the Traditional Approach

Cost item	Traditional	SST	Savings
Equipment investment	Baseline	−20%	Transformer eliminated
Footprint	Baseline	−40%	Much less civil work
Electricity (efficiency)	Baseline	+3–5%	Lower operating cost
Service capacity	Baseline	+20% (utilisation)	Higher revenue

7. Landmark Project Reference

Project	Key data	Significance
CNPC Kunshan station	95%+ efficiency, −40% footprint, −20% investment, 1-day delivery	World-first installation

8. Technical Standards and Compliance

Standard	Scope
GB/T 18487	EV conductive charging
GB/T 27930	Charging communication protocol
GB/T 34120	Energy storage connected to the grid

9. Delivery and Services

Modular factory pre-fabrication
One-day on-site delivery (proven)
Full-lifecycle operation and maintenance with OTA upgrades

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