Simulation Study of the Control Strategy of a DC Inverter Heat Pump Using a DC Distribution Network

Abstract

Photovoltaics, energy storage, direct current and flexibility (PEDF) are important pillars of achievement on the path to manufacturing nearly zero energy buildings (NZEBs). HVAC systems, which are an important part of public buildings, play a key role in adapting to PDEF systems. This research studied the basic principles and operational control strategies of a DC inverter heat pump using a DC distribution network with the aim of contributing to the development and application of small DC distribution systems. Along with the characteristics of a DC distribution network and different operating conditions, a DC inverter heat pump has the ability to adapt to changes in the DC bus voltage and adds flexibility to the system. Theoretical models of the DC inverter heat pump integrated with an ice storage unit were developed. The control strategies of the DC inverter heat pump system considered the influence of both room temperature and varied bus voltage. A simulation study was conducted using MATLAB & Simulink software with simulation results validated by experimental data. The results showed that: (1) The bus fluctuation under the rated working voltage had little effect on the operation of the unit; (2) When the bus voltage was fluctuating from 80%–90% or 105%–107%, the heat pump could still operate normally by reducing the frequency; (3) When the bus voltage was less than 80% or more than 107%, the unit needed to be shut down for the sake of equipment safety, so that the energy storage device could adjust to the sharp decrease or rise of voltage.