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Single-phase traction loads generate negative sequence currents, reactive current and harmonics to the power grid. Modular multilevel converter (MMC) is a better alternative to implement railway power conditioner (RPC), which is connected to 25 kV supply system. A MMC with delta configuration is fit for controlling negative-sequence current because circulating currents across delta-connected clusters provide extra flexibility in unbalance control. A RPC based on delta-connected MMC is developed. Steinmetz theory is used to calculate fundamental frequency phase reference current. Since the obtained fundamental frequency phase reference current always has a 90 degree phase difference with the line voltage, the dc voltage balancing of the MMC is easy to achieve. In addition, harmonic reference current among the three phases are balanced to reduce the total rating of the converter. The design and control of the RPC based on delta-connected MMC are validated by simulation results.

This paper designs a rectifier load simulative generator, which can produce harmonic current, active current and reactive current to test the performance of power quality amelioration equipments conveniently and economically. The characteristics of rectifier circuit with a large inductance loading or with capacitive load are analyzed. The circuit structure and control strategy of the simulative generator are introduced in detail. The energy consumed by the PWM rectifier can be fed back to the grid by the inverter. Thus, the generator can achieve energy conservation, and will need a little power capacity to complete the test. PSIM simulation verify that the proposed generator can simulative actual loads, such as rectifier circuit with a large inductance loading or with capacitive load.

This paper deals with a high-powered, low-loss and digital current disturbance generator. It can produce harmonic current, active current, inductive reactive current and capacitive reactive current, so it is able to simulate kinds of actual industrial situations. By using energy feedback technology, the generator feeds the power consumed by the current disturbance back to the grid. Thus, it can save a lot of energy, and the lab will need less power capacity. The unit of feedback can also compensate the harmonic current and reactive current, so the generator has little impact on the power grid. Simulation result verifies the correctness of analysis and the validity of the project.

Filters are used to implement signal transforms, and filter design is a very important part of the signal processing field. There are currently 2 types of filters available: the finite impulse response (FIR) filter, and the infinite impulse response (IIR) filter. While FIR filters have desirable traits such as stability (an absence of poles), IIR filters are able to generate outputs more efficiently. This paper combines the two types of filters by introducing an output slope trigger, to make a hybrid impulse response (HIR) filter with desirable traits from both FIR and IIR filters

Filters are used to implement signal transforms, and filter design is a very important part of the signal processing field. There are currently 2 types of filters available: the finite impulse response (FIR) filter, and the infinite impulse response (IIR) filter. While FIR filters have desirable traits such as stability (an absence of poles), IIR filters are able to generate outputs more efficiently. This paper combines the two types of filters by introducing a zero-counter, to make a hybrid impulse response (HIR) filter with desirable traits from both FIR and IIR.