Among the core equipment of the energy storage power station, in addition to the battery itself, there is also a key component - PCS (converter) .

Let's start with an analogy: if the energy storage system is likened to an "energy bank ," the PCS plays a key role in storing and accessing electricity. A traditional "grid-following PCS" is like an obedient cashier, operating according to the voltage and frequency set by the grid. A "grid-forming PCS," on the other hand, is more like a bank president (or commander). Even without external grid input, it can independently set voltage and frequency according to pre-set protocols, allowing the microgrid or energy storage station to function as a self-contained system.

1. Network-based PCS

PCS (Power Conversion System), also known as energy storage converter , is the core equipment of the electrochemical energy storage system. It is responsible for realizing the bidirectional conversion between AC and DC power and controlling the charging and discharging process of the battery.

Grid-Forming PCS is an advanced version that not only follows the grid like traditional converters, but also proactively builds voltage and frequency in the event of grid failure or weak grid conditions , providing stable support for the grid.

Simply put, a grid-connected PCS acts like a "virtual synchronous generator ," simulating the inertia and damping characteristics of traditional thermal power units to stabilize the power grid. It can serve as a "regulator" for grid-connected operation and independently build a "microgrid" in the event of a grid failure, making it the "stabilizing force" of power systems in the new energy era.

2. Reasons for Network Construction

rotating generators like thermal and hydropower plants . These inherently possess inertia, allowing them to self-regulate and stabilize the grid. However, today, renewable energy sources like wind and photovoltaic power are connected to the grid through power electronics (such as inverters) . These lack inherent inertia, introducing uncertainty into the grid, often referred to as "poor power quality . "

As the proportion of new energy power generation increases rapidly, the power grid has a "double high" characteristic , namely a high proportion of renewable energy access and a high proportion of power electronic equipment application .

The reduction in traditional synchronous generators has left the power grid feeling like it has lost its backbone, with voltage and frequency fluctuating at will . At this point, if energy storage equipment remains a passive follower, it will be unable to provide effective backup support.

Therefore, the grid-forming PCS came into being. By simulating the characteristics of synchronous generators, it actively contributes inertia, damping and voltage support to the grid, becoming the "new ballast stone" for stabilizing the grid.

3. Core Functions of Network-Based PCS

The core of the grid-based PCS system, which utilizes virtual synchronous generator (VSG) technology, lies in
the virtual synchronous generator algorithm . This algorithm uses mathematical models to simulate the physical characteristics of traditional synchronous generators (such as rotor inertia and damping coefficient), enabling the PCS to respond to inertia and regulate frequency. When power grid fluctuations occur, the grid-based PCS can release or absorb power within milliseconds , rapidly balancing grid supply and demand and preventing frequency collapse.

Dual-mode operation:

When the power grid is operating normally, the grid-connected PCS can act as a "slave machine", following the grid voltage and frequency to provide active/reactive power regulation services.

Off-grid/Island Mode: When the grid fails or is located in a remote area, the grid-connected PCS can independently build voltage and frequency to supply power to local loads and support the "black start" function (i.e. restarting the system without grid support).

Strong overload capacity and anti-disturbance characteristics

A grid-connected PCS typically has a short-term overload capacity of three times the rated current (e.g., for 10 seconds), enabling it to handle short circuits or impact loads in extreme operating conditions. Furthermore, it can accurately identify grid impedance, enabling stable operation in weak grids and minimizing the risk of disconnection.

4. Technical Route of Network-Based PCS

Currently, there are three main technical routes for networking PCS:

String type : Suitable for small and medium-sized energy storage systems, each battery cluster is independently controlled, and operation and maintenance are flexible.

Centralized : Suitable for large-scale energy storage power stations, with high power density, but with the risk of single point failure.

Cascade type : Capacity is increased by connecting multiple modules in parallel, and it is expected to be applied to GW-level energy storage power stations in the future.

The emergence of grid-connected PCS signals a shift in energy storage technology from passive regulation to active support . It serves not only as a safety valve for renewable energy grid integration but also as the intelligent hub of new power systems .