Innovative APF Technology: How Does the Shunt Hybrid APF Based on LQR - PSO Algorithm Solve Power Grid Harmonic Problems?

In the operation of power systems, the surge in nonlinear loads has led to increasingly prominent voltage and current harmonic issues, which not only affect the service life of equipment but also reduce the power supply quality of the power grid. Traditional passive filters have defects such as fixed compensation and easy resonance. However, Active Power Filters (APF) have become the core equipment for harmonic control due to their flexible current injection capability. This article will focus on the shunt hybrid APF based on the LQR - PSO (Linear Quadratic Regulator - Particle Swarm Optimization) algorithm, deeply analyze its technical principles, advantages, and practical application effects, and provide a new direction for enterprise power grid harmonic control.

1. Power Grid Harmonic Troubles: Why Has APF Become the Core of the Solution?

With the increasing proportion of nonlinear loads such as industrial equipment and variable - frequency home appliances in the power grid, the problem of harmonic distortion in current and voltage signals has become more and more serious. Harmonics can cause overheating of transformers, reduce the efficiency of motors, and even trigger misoperation of relay protection devices, directly threatening the stable operation of the power grid.

Traditional harmonic control methods such as LC filters and capacitor banks can suppress harmonics to a certain extent, but they have obvious shortcomings: fixed compensation capacity, unable to adapt to load changes; large volume and high installation cost; easy to resonate with the power grid impedance, which instead aggravates the power supply hidden dangers. APF (Active Power Filter) has completely changed this situation. It can accurately offset harmonics by real - time detecting the harmonic components in the power grid and actively injecting a compensation current with the same magnitude and opposite direction as the harmonic current. Moreover, it has dynamic adjustment capability and can flexibly respond to different load scenarios.

Among various APF topologies, the shunt hybrid APF combines the advantages of active filtering and passive filtering: the APF is responsible for accurately suppressing high - order harmonics, and the capacitor bank undertakes the functions of reactive power compensation and harmonic ripple guidance, which greatly reduces the capacity requirement of the APF and improves the overall control efficiency.

2. Technological Breakthrough: How Does the LQR - PSO Algorithm Optimize the Performance of the Shunt Hybrid APF?

The core competitiveness of the shunt hybrid APF lies in the accuracy of the control algorithm. However, traditional control methods (such as PID and dead - zone control) have problems such as slow response speed and performance degradation under nonlinear loads. The LQR - PSO control algorithm proposed in this article has achieved a leap in the harmonic control effect by optimizing the control parameters of the APF, and its technical logic can be divided into two core links:

1. LQR Controller: Building an Optimal Control Framework for APF

The Linear Quadratic Regulator (LQR) is the "brain" of the APF control. It calculates the optimal feedback gain by minimizing the quadratic performance index (including the weighted integral of state variables and control inputs), ensuring that the compensation current output by the APF accurately tracks the harmonic signal. In the shunt hybrid APF, the control objectives of the LQR are clear:

• Real - time adjustment of the inverter switching state of the APF to generate the required compensation current;
• Suppression of high - frequency ripples generated by the fast switching of the APF to avoid electromagnetic interference to the power grid;
• Maintenance of the stable voltage of the internal capacitor of the APF to ensure the continuous and reliable compensation performance.

The performance of the LQR depends on the values of the state weighting matrix Q and the control weighting matrix R. The Q matrix determines the emphasis on the state variables of the APF (such as filter current and capacitor voltage), and the R matrix balances the energy consumption of the control input. If the traditional "trial - and - error method" is used to adjust Q and R, it is not only time - consuming and labor - intensive but also difficult to find the optimal parameters, which directly limits the harmonic suppression effect of the APF.

2. PSO Algorithm: Achieving "Precise Optimization" for APF Control Parameters

The introduction of the Particle Swarm Optimization (PSO) algorithm has completely solved the problem of LQR parameter tuning. The PSO simulates the foraging behavior of biological groups. Through the iterative search of multiple "particles" (corresponding to the candidate parameter combinations of Q and R) in the solution space, it quickly finds the parameter values that optimize the performance of the APF. Its advantages are reflected in:

• High efficiency: Compared with genetic algorithms and artificial bee colony algorithms, the PSO does not require complex coding and crossover mutation operations. It can search for the optimal solution only by updating the speed and position of particles, which greatly shortens the parameter tuning time;
• Strong robustness: It does not depend on the initial parameter settings. Even if the initial particle distribution is random, it can converge to the global optimal solution, avoiding the performance fluctuation of the APF caused by parameter deviation;
• Good adaptability: It can directly target the topological characteristics of the shunt hybrid APF and take the Integral Absolute Error (IAE) of the filter current and capacitor voltage as the fitness function, ensuring that the optimization goal is highly consistent with the harmonic control needs of the APF.

In the actual simulation, we set 20 search particles and 10 iterations for the shunt hybrid APF, and finally obtained the optimal parameters: the Q matrix is a diagonal matrix diag([5.7267, 7.5435, 21.6203, 0.0001]), and the R matrix is 0.0625. The LQR controller based on these parameters can make the APF output a smoother compensation current and significantly improve the harmonic suppression accuracy.

3. Simulation Verification: What Is the Practical Effect of the LQR - PSO Shunt Hybrid APF?

To verify the technical feasibility, we used MATLAB/Simulink to build a simulation model of the shunt hybrid APF, simulating a power grid scenario with nonlinear loads (6 - pulse diode rectifiers) and linear loads (three - phase RL branches), and compared the performance differences of the APF with and without LQR - PSO control. The results are remarkable:

1. Harmonic Suppression: APF Makes Voltage and Current Signals Smoother

Without LQR - PSO control, although the APF can inject compensation current, due to the high switching frequency, obvious high - frequency ripples appear in the power grid voltage and current signals. The current distortion rate on the source side exceeds 15%, and the voltage fluctuation range on the load side reaches 20%, which cannot meet the requirements of the national standard GB/T 14549 - 1993 for power grid harmonics.

However, the shunt hybrid APF equipped with the LQR - PSO algorithm has completely improved this situation through precise parameter control. The voltage on the source side is stable at 176.7V (rated value), and the current distortion rate is reduced to less than 3%. The voltage on the load side is maintained at 150V (matching the source side voltage), and the current fluctuation range is less than 5%. The signal smoothness is improved by more than 80%, which fully meets the power supply standards of the industrial power grid.

2. Capacity Optimization: APF Injection Current Reduces by 95%, Lowering Energy Consumption

To offset harmonics, the traditional APF needs to inject a compensation current of ±60A, which not only consumes a lot of electric energy but also causes serious heating of the inverter. However, the shunt hybrid APF controlled by LQR - PSO optimizes the compensation strategy, reducing the injection current to ±3A, a decrease of up to 95%! This means that the power loss of the APF is greatly reduced, the service life of the equipment is prolonged, and the occupation of the power grid capacity is reduced, saving electricity costs for enterprises.

3. Response Speed: APF Adapts to Load Changes More Agilely

In the simulation, we simulated a load mutation scenario (nonlinear load suddenly put into operation). The APF without LQR - PSO control takes 0.05 seconds to adjust the compensation current, during which the harmonic concentration of the power grid rises sharply. However, the APF equipped with LQR - PSO has a response time shortened to 0.01 seconds, which can instantly track harmonic changes, avoid voltage sags and current shocks in the power grid, and fully reflect its dynamic adjustment advantages.

4. Industrial Value: What Enlightenment Does APF Technology Bring to Enterprise Power Grid Control?

The shunt hybrid APF based on the LQR - PSO algorithm is not only a technological innovation but also can solve practical pain points for power - intensive enterprises such as manufacturing, chemical industry, and data centers:

• Cost reduction and efficiency improvement: The 95% reduction in APF injection current directly reduces equipment energy consumption and operation and maintenance costs. At the same time, it avoids equipment failures caused by harmonics and reduces downtime losses;
• Compliance with standards: It helps enterprises meet the national standards for power grid harmonics and avoid fines for substandard power supply quality;
• Flexible expansion: The dynamic compensation capability of the APF can adapt to the future load expansion needs of enterprises without frequent replacement of filtering equipment.

In the future, with the large - scale grid connection of new energy power generation (photovoltaic, wind power), the power grid harmonic problem will become more complex. The continuous optimization of APF technology (such as combining AI algorithms to further improve adaptive capabilities) will become the key to ensuring the stable operation of the power grid. For enterprises, laying out APF solutions based on advanced algorithms such as LQR - PSO in advance can not only solve the current harmonic troubles but also lay a foundation for long - term power grid upgrading.

Conclusion

From traditional passive filtering to the technological iteration of APF (Active Power Filter), and then to the injection of new vitality into the shunt hybrid APF by the LQR - PSO algorithm, power grid harmonic control is developing in the direction of "precision, low energy consumption, and high reliability". The shunt hybrid APF proposed in this article has achieved a dual breakthrough in harmonic suppression effect and equipment efficiency through parameter optimization and control optimization, providing a practical solution for improving the power grid quality of enterprises.

If your enterprise is troubled by power grid harmonics or wants to know more about the application details of APF technology, please feel free to contact us. Our professional team will customize an exclusive harmonic control solution for you to make the power grid operation more stable and efficient!

At Hengrong Electrical, we understand that every detail in power control matters. From advanced product design to innovative filtering solutions, we are committed to delivering reliable, efficient, and future-ready technologies. By choosing Hengrong, you gain more than just products — you gain a trusted partner dedicated to helping your business achieve smarter, safer, and greener operations.

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