How Does the Bidirectional Grid Simulator Facilitate the Grid Integration of High-proportion Renewable Energy?

With the accelerated development of green new energy, high-proportion renewable energy grid integration is the only way to achieve the "dual carbon" goal. However, the randomness, intermittency, and volatility of new energy sources (wind and solar) pose unprecedented challenges to grids traditionally designed for stable and controllable power sources.

In this profound energy revolution, the bidirectional grid simulator is increasingly important. They are testing instruments not only in laboratories but also in the "digital foundation" and "pre-show stage" for building a robust and smart grid for the future.

Numerous Difficulties in High-Proportion Renewable Energy Grid Integration

Before delving into solutions, we must clearly understand the problems. When the penetration rate of renewable energy in the grid exceeds 20%, 30%, or even higher, a series of technical challenges will emerge:

System Stability Issues

Traditional grids rely on the huge rotational inertia of synchronous generators to resist instantaneous disturbances and maintain frequency stability. However, wind and solar power, connected to the grid through power electronic devices, do not provide or only provide a small amount of inertia, leading to a decrease in the grid's "resilience" and making it more susceptible to frequency instability due to power fluctuations.

Power Quality Challenges

Frequent switching of power electronic devices introduces harmonics and interharmonics, leading to voltage flicker and waveform distortion. Simultaneously, drastic fluctuations in renewable energy output can cause voltage deviations and frequency fluctuations.

Grid Dispatching Difficulties

The reliance on weather conditions makes renewable energy output forecasting uncertain, posing significant challenges to real-time power balance and dispatch planning.

Fault Ride-Through Capability

When grid faults such as short circuits occur, traditional generators provide short-circuit currents to help protection devices identify and isolate the fault. However, renewable energy inverters may disconnect from the grid during faults or provide significantly different short-circuit current characteristics, posing new requirements for the coordination of relay protection systems.

Faced with these challenges, we cannot "cross the river by feeling the stones" in a real power grid. A single fault could lead to widespread blackouts, causing enormous economic losses and social impact. Therefore, it is essential to conduct pilot tests in the laboratory, and the bidirectional grid simulator is the core of this "pilot laboratory."

What is a Bidirectional Grid Simulator?

Simply put, a bidirectional grid simulator is a highly precise, programmable power supply device. The fundamental difference between it and ordinary power sources lies in the word "bidirectional."

Traditional power sources or loads can only generate power (simulating a generator) or absorb power (simulating a load).

A bidirectional power grid simulator can both generate power, simulating the characteristics of various generators (including thermal, hydro, wind, and solar power), and absorb power, simulating the operating state of various loads (from residential electricity to large factories) and even the entire power grid. It can switch quickly and seamlessly across four quadrants, precisely controlling voltage, current, frequency, and phase.

More importantly, it is a real-time simulation platform. Researchers can connect real equipment (such as solar inverters, wind power converters, energy storage converters, and electric vehicle charging stations) to the simulator and then build a highly realistic "digital power grid" environment within it.

This digital power grid can simulate:

l   Normal power grid operating conditions: such as steady-state operation and minor fluctuations in frequency and voltage.

l   Extreme power grid events: such as voltage drops caused by lightning strikes, line short-circuit faults, and rapid frequency changes.

l   Future power grid scenarios: such as weak grid conditions under high-proportion renewable energy integration.

In this way, the tested equipment no longer faces a rigid testing standard, but operates in a "living," dynamically changing virtual power grid. The bidirectional power grid simulator thus transforms from a passive "actor" into an "all-around director" capable of orchestrating various complex power grid scenarios.

Four Core Application Scenarios of Bidirectional Power Grid Simulators

The value of bidirectional power grid simulators is specifically reflected in the following key areas:

1. An "Accelerator" for Equipment R&D and Certification

Before photovoltaic inverters, wind power converters, and energy storage PCS are launched on the market, they must pass rigorous grid adaptability certifications (such as China's NB/T 32004 and Germany's VDE-AR-N 4105). Bidirectional power grid simulators can accurately reproduce all test waveforms specified in the standards (such as high/low voltage ride-through, frequency adaptability, and harmonic testing), significantly shortening the R&D cycle and ensuring that new products meet grid connection requirements, thereby improving the grid's "inclusivity" for renewable energy from the source.

2. A Testing Ground for Breakthroughs in Grid-Based Technology

To address the lack of grid inertia, the industry has proposed "grid-based" technology. Unlike traditional grid-following inverters that passively follow the grid, grid-based inverters can actively provide voltage and frequency support, much like synchronous generators, and even construct a stable grid "out of thin air."

A bidirectional grid simulator is the only effective tool for developing and validating grid-based technology. It can simulate a zero-inertia, extremely fragile "weak grid" in the laboratory, allowing researchers to test whether grid-based inverters can truly form an independent grid, provide inertia and damping, and evaluate the stability of multiple grid-based devices operating in parallel.

3. An Optimizer for Energy Storage System Integration and Control

Energy storage is key to smoothing the fluctuations in renewable energy. But how should energy storage systems be configured? How should control strategies be formulated? A bidirectional grid simulator can simulate real-world scenarios of combined wind and solar power output, connecting real energy storage converters and battery systems to test their performance under various application modes such as peak shaving, valley filling, fluctuation smoothing, and frequency regulation. Through repeated simulations and optimizations, the optimal battery capacity, power configuration, and control algorithm can be found, maximizing the economic and technical benefits of the energy storage system.

4. A "Predictive Crystal Ball" for Grid Planning and Operation

Before connecting a new wind farm or photovoltaic power station to the actual grid, grid companies can use a real-time simulation platform based on a two-way grid simulator to conduct hardware-in-the-loop testing. They connect the real power station controller to the simulator, which runs a detailed grid model of the target connection area. In this way, they can anticipate the impact of the power station's connection on local voltage, line power flow, and system stability, assessing whether additional energy storage, SVG, and other supporting equipment are needed, thus making more scientific and safer decisions.

Looking to the Future: From Testing Tool to the Core of the Grid's "Digital Twin"

With the development of artificial intelligence and big data technologies, the role of the two-way grid simulator will be further enhanced. It will be deeply integrated with meteorological data and real-time grid operation data to construct a "digital twin grid" that operates synchronously with the physical grid and interacts with the real world.

In this digital twin, we can:

l   Conduct grid resilience simulations under extreme weather conditions and formulate defense strategies in advance.

l   Simulating market transactions optimizes the absorption of renewable energy.

l   Training dispatchers to handle various emergencies in a virtual environment.

Conclusion

The future power grid with a high proportion of renewable energy is a magnificent energy system engineering project. We can no longer rely on trial and error to move forward, but must rely on forward-looking design, accurate forecasting, and thorough verification. The two-way grid simulator is precisely such a powerful tool that gives us "foresight." It builds a solid digital bridge between us and a clean, stable, and efficient energy future. Silently, it is conducting the most crucial "stress test" and "perfect rehearsal" for our bright future world.